Bump github.com/google/trillian from 1.4.1 to 1.4.2 in /hack/tools

Bumps [github.com/google/trillian](https://github.com/google/trillian) from 1.4.1 to 1.4.2.
- [Release notes](https://github.com/google/trillian/releases)
- [Changelog](https://github.com/google/trillian/blob/master/CHANGELOG.md)
- [Commits](google/trillian@v1.4.1...v1.4.2)

---
updated-dependencies:
- dependency-name: github.com/google/trillian
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

hack/tools/go.mod

@@ -7,6 +7,6 @@ require (
 	github.com/dvyukov/go-fuzz v0.0.0-20210914135545-4980593459a1
 	github.com/elazarl/go-bindata-assetfs v1.0.1 // indirect
 	github.com/go-swagger/go-swagger v0.29.0
-	github.com/google/trillian v1.4.1
+	github.com/google/trillian v1.4.2
 	github.com/stephens2424/writerset v1.0.2 // indirect
 )