Update sbt-dynver to 5.1.0 #983

Job	Run time
Docs	2m 55s
Checks	1m 56s
Compile and test (2.12.20, 8)	4m 5s
Compile Benchmarks	1m 44s
Gradle tests	3m 25s
Compile and test (2.12.20, 11)	3m 56s
Maven tests	2m 54s
sbt scripted tests (gen-scala-server, 2.12)	8m 19s
Compile and test (2.12.20, 17)	4m 2s
sbt scripted tests (gen-java, 2.12)	3m 49s
Compile and test (2.12.20, 21)	3m 42s
Compile and test (2.13.15, 8)	4m 31s
Compile and test (2.13.15, 11)	4m 45s
Compile and test (2.13.15, 17)	4m 26s
Compile and test (2.13.15, 21)	4m 16s
Compile and test (3.3.4, 8)	4m 40s
Compile and test (3.3.4, 11)	4m 40s
Compile and test (3.3.4, 17)	4m 45s
Compile and test (3.3.4, 21)	4m 14s
	1h 17m 4s

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