[fix][java]Add missing generated annotation to Authentication.mustach… #2481

Job	Run time
Gradle tests (samples/client/petstore/java/native)	1m 4s
Gradle tests (samples/openapi3/client/petstore/java/jersey2-java8)	1m 3s
Gradle tests (samples/client/petstore/java/jersey2-java8)	1m 6s
Gradle tests (samples/client/petstore/java/webclient-swagger2)	1m 7s
Gradle tests (samples/client/petstore/java/jersey2-java8-localdatetime)	1m 4s
Gradle tests (samples/client/petstore/java/native-jakarta)	1m 0s
Gradle tests (samples/client/petstore/java/okhttp-gson-group-parameter)	1m 3s
Gradle tests (samples/openapi3/client/extensions/x-auth-id-alias/java/jersey2-java8)	1m 2s
Gradle tests (samples/openapi3/client/petstore/java/jersey2-java8-special-characters)	1m 10s
Gradle tests (samples/client/petstore/java/okhttp-gson)	1m 9s
	10m 48s

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