Bump grpc.version from 1.66.0 to 1.68.0

Bumps `grpc.version` from 1.66.0 to 1.68.0.

Updates `io.grpc:grpc-core` 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-netty-shaded` 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-netty` 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` 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)

Updates `io.grpc:grpc-grpclb` 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-core
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: io.grpc:grpc-netty-shaded
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: io.grpc:grpc-netty
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: io.grpc:grpc-protobuf
  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
- dependency-name: io.grpc:grpc-grpclb
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

dubbo-extensions-dependencies-bom/pom.xml

@@ -122,7 +122,7 @@
         <slf4j_version>1.7.36</slf4j_version>
         <grizzly_version>2.4.4</grizzly_version>
         <jetcd_version>0.7.7</jetcd_version>
-        <grpc.version>1.66.0</grpc.version>
+        <grpc.version>1.68.0</grpc.version>
         <etcd_launcher_version>0.7.7</etcd_launcher_version>
         <netty4_version>4.1.113.Final</netty4_version>
         <consul_process_version>2.2.1</consul_process_version>