Fixes https://github.com/playframework/play-grpc/issues/468 (#197) #588

Job	Run time
Compile Benchmarks	1m 8s
Docs	2m 15s
Checks	1m 36s
Compile and test (2.12.18, 8)	3m 40s
Gradle tests	3m 35s
Compile and test (2.12.18, 11)	3m 43s
Maven tests	2m 35s
Compile and test (2.13.11, 8)	4m 28s
sbt scripted tests (gen-scala-server, 2.12)	7m 59s
Compile and test (2.13.11, 11)	4m 7s
sbt scripted tests (gen-java, 2.12)	3m 10s
Compile and test (3.3.1, 8)	5m 13s
Compile and test (3.3.1, 11)	4m 44s
	48m 13s

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