build(deps): bump golang.org/x/tools from 0.20.0 to 0.21.0 in /tools

Bumps [golang.org/x/tools](https://github.com/golang/tools) from 0.20.0 to 0.21.0.
- [Release notes](https://github.com/golang/tools/releases)
- [Commits](golang/tools@v0.20.0...v0.21.0)

---
updated-dependencies:
- dependency-name: golang.org/x/tools
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

tools/go.mod

@@ -2,7 +2,7 @@ module go.abhg.dev/goldmark/mermaid/tools
 
 go 1.19
 
-require golang.org/x/tools v0.20.0
+require golang.org/x/tools v0.21.0
 
 require (
 	golang.org/x/mod v0.17.0 // indirect

tools/go.sum

@@ -2,5 +2,5 @@ golang.org/x/mod v0.17.0 h1:zY54UmvipHiNd+pm+m0x9KhZ9hl1/7QNMyxXbc6ICqA=
 golang.org/x/mod v0.17.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/sync v0.7.0 h1:YsImfSBoP9QPYL0xyKJPq0gcaJdG3rInoqxTWbfQu9M=
 golang.org/x/sync v0.7.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
-golang.org/x/tools v0.20.0 h1:hz/CVckiOxybQvFw6h7b/q80NTr9IUQb4s1IIzW7KNY=
-golang.org/x/tools v0.20.0/go.mod h1:WvitBU7JJf6A4jOdg4S1tviW9bhUxkgeCui/0JHctQg=
+golang.org/x/tools v0.21.0 h1:qc0xYgIbsSDt9EyWz05J5wfa7LOVW0YTLOXrqdLAWIw=
+golang.org/x/tools v0.21.0/go.mod h1:aiJjzUbINMkxbQROHiO6hDPo2LHcIPhhQsa9DLh0yGk=