[TASK] Improve styling of infobox in ImageManipulationElement

The cropping element shows an information if no dimensions are known.
The styling of this information is now improved.

Resolves: #86429
Releases: master, 8.7
Change-Id: I28b6e4da560e591a57e6c849488f59ddf5cd5736
Reviewed-on: https://review.typo3.org/58441


Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Josef Glatz <josef.glatz@typo3.org>
Tested-by: Josef Glatz <josef.glatz@typo3.org>
Reviewed-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Tested-by: Tymoteusz Motylewski <t.motylewski@gmail.com>