Delete ancient 'managing PRs' flowchart

- This diagram was really old and didn't reflect the current practices
  (a lot more things are automated now, hurray).
- Anything we replace it with will get outdated fast too.
- Also delete the diagramming docs since I don't believe we have made
  another diagram since this one which got out of date and forgotten
  about since it was a DrawIO SVG and not easily editable as code.
- If we want diagrams these days, we can use Mermaid which is
  diagrams-as-code.

.editorconfig

@@ -16,11 +16,6 @@ trim_trailing_whitespace = true
 # trailing whitespace is crucial for patches
 trim_trailing_whitespace = false
 
-[**.drawio.svg]
-indent_size = unset
-indent_style = unset
-insert_final_newline = false
-
 [**.md]
 trim_trailing_whitespace = true
 x-soft-wrap-text = true

docs/Diagram-Guidelines.md

@@ -1,45 +0,0 @@
-# Diagram Guidelines
-
-## Preferred file format
-
-For complex diagrams, use the `.drawio.svg` format.
-
-Files with the `.drawio.svg` extension are SVG files with embedded [draw.io](https://www.diagrams.net/) source code. Using that format lends itself to a developer-friendly workflow: it is valid SVG, plays well with `git diff` and can be edited in lock-step using various online and offline flavours of draw.io. If you use VS Code, you can use an [extension](https://marketplace.visualstudio.com/items?itemName=hediet.vscode-drawio) for draw.io integration.
-
-Files in the `.drawio.svg` format can be processed offline.
-
-## Embedding a diagram into Markdown
-
-To embed a `.drawio.svg` file into Markdown, use the same syntax as for any image. Example: `![My diagram](my-diagram.drawio.svg)`
-
-Mind that GitHub doesn’t allow styling in Markdown documents. Where styling is allowed (e.g. in the exported brew.sh version of the documentation), always set a background colour of `white` for the diagram. That’s the colour draw.io assumes, and keeps the diagram easy to read in dark mode without further customization. You can use the CSS selector `img[src$=".drawio.svg"]` for styling.
-
-## Example
-
-Example for an SVG image embedded into Markdown:
-
-```md
-![Example diagram: Managing Pull Requests](assets/img/docs/managing-pull-requests.drawio.svg)
-```
-
-Result:
-
-![Example diagram: Managing Pull Requests](assets/img/docs/managing-pull-requests.drawio.svg)
-
-Example for styling (where allowed):
-
-```css
-img[src$=".drawio.svg"] {
-  background-color: white;
-  margin-bottom: 20px;
-  padding: 5%;
-  width: 90%;
-}
-
-@media (prefers-color-scheme: dark) {
-  img[src$=".drawio.svg"] {
-    filter: invert(85%);
-    -webkit-filter: invert(85%);
-  }
-}
-```

docs/Homebrew-homebrew-core-Maintainer-Guide.md

@@ -25,7 +25,7 @@ For most PRs that make formula modifications, you can simply approve the PR and
 
 Certain PRs may not be merged automatically by [@BrewTestBot](https://github.com/BrewTestBot), even after they've been approved. This includes PRs with the `new formula`, `automerge-skip`, and `linux-only` labels. To trigger a merge for these PRs, run `brew pr-publish`.
 
-PRs modifying formulae that don't need bottles or making changes that don't require new bottles to be pulled should use GitHub's squash & merge or rebase & merge workflows. See the [table below](#how-to-merge-without-bottles) for more details.
+PRs modifying formulae that don't need bottles or making changes that don't require new bottles to be pulled should use GitHub's squash & merge or rebase & merge workflows.
 
 Otherwise, you should use `brew pr-pull` (or `rebase`/`cherry-pick` contributions).
 
@@ -35,10 +35,6 @@ Cherry-picking changes the date of the commit, which kind of sucks.
 
 Don’t `merge` unclean branches. So if someone is still learning `git` and their branch is filled with nonsensical merges, then `rebase` and squash the commits. Our main branch history should be useful to other people, not confusing.
 
-Here’s a flowchart for managing a PR which is ready to merge:
-
-![Flowchart for managing pull requests](assets/img/docs/managing-pull-requests.drawio.svg)
-
 Only one maintainer is necessary to approve and merge the addition of a new or updated formula which passes CI. However, if the formula addition or update proves controversial the maintainer who adds it will be expected to answer requests and fix problems that arise with it in future.
 
 ### How to merge without bottles