[TASK] Remove @internal from configuration exceptions

This change removes the `@internal` declaration from two exceptions
thrown by `ExtensionConfiguration->get()` which is used by extension
authors when fetching the extension configuration as those may be
caught by extension code.

Releases: master, 11.5
Resolves: #96657
Change-Id: I8c90cd62c5558487cd32a7b7bf4c0dec7bb5efb0
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73162


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benjamin Franzke <bfr@qbus.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>