Add missing excludes for the unknown file extensions to the license plugin #5850

Job	Run time
sample_operators_tests (sample-operators/mysql-schema)	3m 19s
sample_operators_tests (sample-operators/tomcat-operator)	3m 45s
sample_operators_tests (sample-operators/webpage)	3m 48s
sample_operators_tests (sample-operators/leader-election)	4m 5s
	14m 57s

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