Pin versions of actions in the workflow (#631) #892

Job	Run time
tests (Unit tests, test jacoco:report)	4m 56s
tests (Style check, compile com.mycila:license-maven-plugin:check pmd:pmd pmd:cpd pmd:check pmd:c...	5m 6s
tests (OSGi integration, install -P docker-integration-test,osgi-integration-tests -DskipUTs, osg...	5m 29s
tests (Standalone integration 4.0, verify -P docker-integration-test,standalone-integration-tests...	9m 40s
tests (Standalone integration 4.1, verify -P docker-integration-test,standalone-integration-tests...	11m 52s
tests (Standalone integration 5.0-alpha1, verify -P docker-integration-test,standalone-integratio...	11m 42s
tests (Python integration, verify -P docker-integration-test,python-integration-tests -DskipUTs, ...	6m 48s
	55m 33s

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