chore(global-writes): fix subtab container styles

[gribnoysup]

Some small fixes for the global-writes tab conatiner:

• WorkspaceContainer component should not be wrapped in anything, the intent is for it to always just take all the availble space in the tab, otherwise the shadow and scroll it renders looks weird and kinda broken

Before	After

• Loading spinner was off-center because of the max width for the content it was rendered in, I also removed the vertical centering, we usually do a margin from the top (see CRUD for example) so that on bigger screens it's not showing up too close to the bottom, it looks a bit off and inconsistent with other tabs in the app

Before	After