[BUGFIX] Fix auto width in extension icon in EM

If an extension is using a svg icon with no explicit height/width obviously,
then the extension manager shows the icon on the full width of the
table column, making it not only inconsistent but impossible to read the
extension text.

The patch removes the "width: auto" style in CSS.

Resolves: #76381
Releases: master, 7.6
Change-Id: Idb9cfa9bd5720920f67b35d2dada6b21a469a1db
Reviewed-on: https://review.typo3.org/49315


Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>