chore(gradle): bump io.grpc:grpc-bom from 1.58.0 to 1.68.0

Bumps [io.grpc:grpc-bom](https://github.com/grpc/grpc-java) from 1.58.0 to 1.68.0.
- [Release notes](https://github.com/grpc/grpc-java/releases)
- [Commits](grpc/grpc-java@v1.58.0...v1.68.0)

---
updated-dependencies:
- dependency-name: io.grpc:grpc-bom
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

gradle/libs.versions.toml

@@ -31,7 +31,7 @@ google-findbugs = "3.0.2"
 google-java-allocation-instrumenter = "3.3.4"
 groovy = "3.0.22"
 # Only bump this in concert with boringssl
-grpc = "1.58.0"
+grpc = "1.68.0"
 guava = "33.3.1-jre"
 gwt = "2.11.0"
 # used by GwtTools