[BUGFIX] Use less aggressive string replace in IRRE headers

The current way of cutting out the _header portion of an IRRE header was
too aggressive and might cut of unwanted parts of the id attribute.
We change the regex to only check on the end of the string to fix this.

Resolves: #54530
Releases: master
Change-Id: I935d93ad1eca7f2599ab6a91845e2fe363a9719a
Reviewed-on: http://review.typo3.org/44104


Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>