[TASK] Remove superfluous parens in sysexts css_styled_content - feedit

Removes superfluous parenthesis in sysexts "css_styled_content",
"extensionmanager", "extra_page_cm_options" and "feedit".

Change ("a" . "b") . "c" into "a" . "b" . "c" using the lex-pass tool.

Change-Id: I9ec62d6b2782e349cef447c7a9c87f4a4fbc2585
Resolves: #40964
Related: #40095
Reviewed-on: http://review.typo3.org/14623
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert