Bump io.grpc:grpc-bom from 1.66.0 to 1.68.0 (#9433)

Bumps [io.grpc:grpc-bom](https://github.com/grpc/grpc-java) from 1.66.0 to 1.68.0.
- [Release notes](https://github.com/grpc/grpc-java/releases)
- [Commits](https://github.com/grpc/grpc-java/commits)

---
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]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

build.gradle.kts

@@ -30,7 +30,7 @@ plugins {
 
 // Can't use typed variable syntax due to Dependabot limitations
 extra.apply {
-    set("grpcVersion", "1.66.0")
+    set("grpcVersion", "1.68.0")
     // Override jooq version since the official gradle plugin is on in 3.19.x, remove if not needed
     // with the next springboot release
     set("jooq.version", "3.19.6")