build(deps): bump mvdan.cc/gofumpt

Bumps [mvdan.cc/gofumpt](https://github.com/mvdan/gofumpt) from 0.11.1-0.20260823225713-28272d18f832 to 0.12.0.
- [Release notes](https://github.com/mvdan/gofumpt/releases)
- [Changelog](https://github.com/mvdan/gofumpt/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mvdan/gofumpt/commits/v0.12.0)

---
updated-dependencies:
- dependency-name: mvdan.cc/gofumpt
  dependency-version: 0.12.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

go.mod

@@ -155,7 +155,7 @@ require (
 	golang.org/x/sys v0.47.0
 	golang.org/x/tools v0.49.0
 	honnef.co/go/tools v0.8.1
-	mvdan.cc/gofumpt v0.11.1-0.20260823225713-28272d18f832
+	mvdan.cc/gofumpt v0.12.0
 	mvdan.cc/unparam v0.0.0-20260823230713-2fa3d841b0c8
 )