SpringBoot fix for "BootJar.getConfigurations() should not be public API" #23527

Changes: This a fix for BootJar.getConfigurations() should not be public API #23527 deprecated the method. All tests have passed and the method is no longer in the public API.

Comment From: philwebb

Thanks for the pull-request, but it's easier if we handle this one. We'll need to apply it to an older branch and also document the deprecation.

Comment From: somayaj

Sounds good. Thanks