Bump alpine from 3.21.2 to 3.21.3 in /src/test/resources/org/jvnet/hudson/plugins/platformlabeler/alpine/3.21.2

Bump alpine from 3.21.2 to 3.21.3 in /src/test/resources/org/jvnet/hudson/plugins/platformlabeler/alpine/3.21.2 #889