Bump io-grpc from 1.66.0 to 1.68.0

Bumps `io-grpc` from 1.66.0 to 1.68.0.

Updates `io.grpc:grpc-okhttp` 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)

Updates `io.grpc:grpc-protobuf-lite` 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)

Updates `io.grpc:grpc-stub` 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-okhttp
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: io.grpc:grpc-protobuf-lite
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: io.grpc:grpc-stub
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -2,7 +2,7 @@
 androidx-lifecycle = "2.9.0-alpha01"
 ben-manes-versions = "0.51.0"
 google-firebase-bom = "32.7.0"
-io-grpc = "1.66.0"
+io-grpc = "1.68.0"
 jlleitschuh-ktlint = "12.1.1"
 kotlin = "2.0.20"
 kotlinx-coroutines = "1.9.0"