[TASK] Remove last bits of gdlib_2 setting

Support for gdlib version 1 was removed with core version 4.4.
The patch removes the last code fragments where the old GFX/gdlib_2
setting was used and activates a key in ext:install to remove
the setting from LocalConfiguration.

Change-Id: Icec65f13468306b80a575996a23cdbbbd21d715c
Resolves: #49335
Related: #22687
Related: #49299
Releases: 6.2
Reviewed-on: https://review.typo3.org/21582
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring
Reviewed-by: Markus Klein
Reviewed-by: Philipp Gampe
Reviewed-by: Stefan Neufeind
Tested-by: Markus Klein