rebase: bump google.golang.org/grpc from 1.47.0 to 1.48.0

Bumps [google.golang.org/grpc](https://github.com/grpc/grpc-go) from 1.47.0 to 1.48.0.
- [Release notes](https://github.com/grpc/grpc-go/releases)
- [Commits](https://github.com/grpc/grpc-go/compare/v1.47.0...v1.48.0)

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

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

vendor/google.golang.org/grpc/internal/balancer/gracefulswitch/gracefulswitch.go

@@ -193,6 +193,8 @@ func (gsb *Balancer) ExitIdle() {
 		ei.ExitIdle()
 		return
 	}
+	gsb.mu.Lock()
+	defer gsb.mu.Unlock()
 	for sc := range balToUpdate.subconns {
 		sc.Connect()
 	}