Bump google.golang.org/grpc from 1.56.0 to 1.56.2

Bumps [google.golang.org/grpc](https://github.com/grpc/grpc-go) from 1.56.0 to 1.56.2.
- [Release notes](https://github.com/grpc/grpc-go/releases)
- [Commits](https://github.com/grpc/grpc-go/compare/v1.56.0...v1.56.2)

---
updated-dependencies:
- dependency-name: google.golang.org/grpc
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

vendor/google.golang.org/grpc/clientconn.go

@@ -1033,8 +1033,10 @@ func (ac *addrConn) updateAddrs(addrs []resolver.Address) {
 
 	// We have to defer here because GracefulClose => Close => onClose, which
 	// requires locking ac.mu.
-	defer ac.transport.GracefulClose()
-	ac.transport = nil
+	if ac.transport != nil {
+		defer ac.transport.GracefulClose()
+		ac.transport = nil
+	}
 
 	if len(addrs) == 0 {
 		ac.updateConnectivityState(connectivity.Idle, nil)