upgrade sbt version to 1.9.9 #725

Job	Run time
Compile Benchmarks	3m 48s
Checks	4m 36s
Docs	5m 28s
Compile and test (2.12.18, 8)	9m 50s
Gradle tests	5m 32s
sbt scripted tests (gen-scala-server, 2.12)	10m 8s
Maven tests	5m 3s
sbt scripted tests (gen-java, 2.12)	5m 59s
Compile and test (2.12.18, 11)	6m 47s
Compile and test (2.13.12, 8)	4m 53s
Compile and test (2.13.12, 11)	7m 37s
Compile and test (3.3.1, 8)	8m 2s
Compile and test (3.3.1, 11)	7m 45s
	1h 25m 28s

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