Use generic scss for com_installer and com_joomaupdate

[chmst]

Summary of Changes

Removed scss files for com_installer and com_joomlaupdate to keep the number of scss files small. Add class "options-fieldset" to fieldsets

Testing Instructions

For com_joomlaupdate testing requires the simulation of different special use cases, where the different layouts are displayed.

[brianteeman]

If the only reason was to keep the number of scss files low it's not a good idea as there is no real benefit

[chmst]

The main reason is that one single class is better to maintain, it avoids different views when the layout of the blocks in option views is changed. Less files in scss folder is a nice side effect.

BTW: These layouts seem to be old, they still use Layout tables. But this is not in scope here

[brianteeman]

Did you test this? The PR removes a class "uploadform". This is used as an identifier in the javascript

[chmst]

Thank you!