[HttpKernel] Remove unused method Kernel::isClassInActiveBundle

Follow-up of #11869
feature #12854 [3.0][HttpKernel] Remove unused method Kernel::isClassInActiveBundle (hacfi)

This PR was merged into the 3.0-dev branch.

Discussion
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[3.0][HttpKernel] Remove unused method Kernel::isClassInActiveBundle

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | yes, if using isClassInActiveBundle (not used by Symfony itself)
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #11652
| License       | MIT
| Doc PR        | - (Not mentioned in the docs)

Follow-up of #11869

Commits
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91dcca4 [HttpKernel] Remove unused method Kernel::isClassInActiveBundle