Bump grpcio-testing from 1.54.0 to 1.54.2 in /test/environment/grpc

Bumps [grpcio-testing](https://grpc.io) from 1.54.0 to 1.54.2.

---
updated-dependencies:
- dependency-name: grpcio-testing
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

test/environment/grpc/requirements.txt

@@ -2,4 +2,4 @@ grpcio-tools==1.54.0
 grpcio==1.54.2
 grpcio-reflection==1.54.2
 grpcio-health-checking==1.54.2
-grpcio-testing==1.54.0
+grpcio-testing==1.54.2