Set max width on user preference inputs

What does this MR do and why?

• Sets max width on settings inputs

What does this MR not do?

Fix line with across all settings (the text, for example, is still full-width)

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Go to user > user preferences
• Inputs should have a smaller width (on both fixed and fluid layout preferences)
• Rest of text (labels, help text, etc) should not be affected

UX Paper Cuts 16.3 → Settings UI, part 2 (#417912 - closed)