[BUGFIX] Fix call to formWidth in template module

DocumentTemplate::formWidth() is not available and should be removed
anyway.
Replace the calls by direct usage of style attribute.

Change-Id: I141a4b74424c2ecd0a1341228856e23c8c42f20e
Resolves: #72854
Releases: master
Reviewed-on: https://review.typo3.org/46127


Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Frank Nägler <frank.naegler@typo3.org>
Tested-by: Frank Nägler <frank.naegler@typo3.org>