Remove height: auto !important styles for .content img

Fixes shields and phantom overlays in mobile VE.

These rules were moved from #content img in 8d0e4aa7. They do not seem
to affect Special:Uploads or Special:UserProfile in any way.

Unfortunately, I don't know what Nicole Sullivan says because of
[citation needed]. There are no other comments specifying what exactly
height: auto !important was for, so it seems like a good idea to remove
it and bring it back somewhere else if necessary.

Bug: 60841

Change-Id: I2157134db93c9cf87bcca76135a34201ca8fe3c5
Merge "Remove height: auto !important styles for .content img"