This is in series of refactoring of code for realm logo settings.
Further, we will remove ids from the template as well and simply use
general classes (.day-settings and .night-settings) to identify to which
theme-mode particular element belongs i.e. day or night as we did in this
change.
- These ids will further be used to represent each section concisely and
deduplicating code.
- Also, removed `realm-night-logo-section` class as it was redundant.
When we add Plus, the first sentence should change to "Available on Zulip
Standard and Plus".
I copied the styling of .tip out of expediency, but it's also possible that
long term we'll want only 1 tip-like box styling.
The hover styling is a bit random, but I tried to copy other hover styles I
found in settings.scss.
Note that this renames .upgrade_realm_plan_type_suggestion to .upgrade-tip.
Pragati Agrawal
Rishi Gupta
Anders Kaseorg