Fix new CI failure (#230)

Although the fix in #228 passed CI on the PR, it failed on `main`. As
far as I can tell, it seems to be inconsistent depending on which GitHub
runner gets assigned to the job. After further experimentation and
digging, it looks like `colima` [had some breaking changes from 0.5.x ->
0.6.x](https://github.com/abiosoft/colima/releases/tag/v0.6.6) which
require `colima delete` to be run prior to starting. The changes in this
PR address the issue, and I've re-run CI multiple times on this PR to
try on multiple runners.

Thankfully, we'll be able to axe this setup once we switch to the new
conformance runner.

Error:

```
==> Pouring [email protected]_1.ventura.bottle.tar.gz
Error: The `brew link` step did not complete successfully
The formula built, but is not symlinked into /usr/local
Could not symlink bin/python3.12
Target /usr/local/bin/python3.12
already exists. You may want to remove it:
  rm '/usr/local/bin/python3.12'
```

.github/workflows/ci.yaml

@@ -68,12 +68,9 @@ jobs:
       - name: Set up docker (missing on macOS GitHub runners)
         # https://github.com/actions/runner-images/issues/2150
         run: |
-          rm '/usr/local/bin/2to3-3.12'
-          rm '/usr/local/bin/idle3.12'
-          rm '/usr/local/bin/pydoc3.12'
-          brew unlink [email protected]
+          brew unlink [email protected] && brew link --overwrite [email protected]
           brew install docker colima
-          colima start
+          colima delete && colima start
       - name: Run tests
         run: make test
   run-swiftlint: