[TASK] Deprecate enableConcatenateFiles

Also config.concatenateJsAndCss TypoScript is replaced
with concatenateCss and concatenateJs since TYPO3 v6.0,
and can now be deprecated.

Resolves: #65578
Releases: master
Change-Id: I23ee9637a3c880c67a93a6f9771a9bfab5ed6ac3
Reviewed-on: https://review.typo3.org/57629


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>