Remove "Delete" and "Create Folder" actions from sidebar

The number of actions in Gwenview's sidebar currently causes the main window with default settings to be taller than the amount of vertical space available for users with 1366x768 screens and the default 44px bottom panel. In this configuration, Gwenview's footer becomes inaccessible, breaking various parts of the app's functionality, such as the ability to zoom and switch sidebar tabs.

I know what you're about to say. Yes, it's 2023 and people are still using 1366x768 screens. Unfortunately they still will be for a long time; this is the second most common screen resolution for desktop/laptop computers worldwide. See https://gs.statcounter.com/screen-resolution-stats/desktop/worldwide

We could fix this by making the sidebar actions list scrollable, but that's kind of an ugly solution as scrollable lists of actions present an unpleasant UX overall.

So instead, let's remove two actions from the sidebar:

• The "Delete" action, which is actively dangerous to the user's data and should definitely not live next to safe actions.
• The "Create Folder" action is super niche in purpose as Gwenview is not really meant to be a file management app.

Both actions remain visible in the GUI menu structure and accessible via keyboard shortcut. BUG: 458987 FIXED-IN: 23.08

@teams/vdg

Now it fits with only a few insignificant pixels cut off on the bottom: