chore: set version to 5.4.0-SNAPSHOT #7403

Job	Run time
sample_operators_tests (sample-operators/tomcat-operator)	4m 26s
sample_operators_tests (sample-operators/leader-election)	4m 51s
sample_operators_tests (sample-operators/mysql-schema)	4m 13s
sample_operators_tests (sample-operators/webpage)	4m 23s
sample_operators_tests (sample-operators/operations)	9m 20s
	27m 13s

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