Update maven-core, maven-plugin-api to 3.9.9 #928

Job	Run time
Docs	2m 35s
Compile Benchmarks	1m 12s
Checks	1m 44s
Compile and test (2.12.19, 8)	3m 49s
Gradle tests	3m 20s
Compile and test (2.12.19, 11)	3m 49s
Maven tests	2m 45s
Compile and test (2.12.19, 17)	3m 41s
sbt scripted tests (gen-scala-server, 2.12)	7m 46s
Compile and test (2.12.19, 21)	3m 35s
sbt scripted tests (gen-java, 2.12)	3m 38s
Compile and test (2.13.14, 8)	4m 38s
Compile and test (2.13.14, 11)	4m 9s
Compile and test (2.13.14, 17)	4m 24s
Compile and test (2.13.14, 21)	4m 2s
Compile and test (3.3.3, 8)	4m 45s
Compile and test (3.3.3, 11)	4m 25s
Compile and test (3.3.3, 17)	4m 29s
Compile and test (3.3.3, 21)	3m 58s
	1h 12m 44s

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