bump: protobuf 3.21.12 #1113

Job	Run time
Checks	4m 8s
Compile and test (2.13)	6m 20s
Compile Benchmarks	3m 1s
Compile and test (3.3)	7m 43s
Docs	4m 23s
Gradle tests	3m 41s
Maven tests	3m 22s
sbt scripted tests (gen-scala-server, 2.13)	11m 25s
sbt scripted tests (gen-java, 2.13)	6m 29s
sbt scripted tests (scala-2_13, 2.13)	5m 57s
sbt scripted tests (scala3, 3.3)	4m 51s
	1h 1m 20s

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