Fix some build warnings

[litetex]

What is it?

• Bugfix (user facing)
• Feature (user facing)
• Codebase improvement (dev facing)
• Meta improvement to the project (dev facing)

Description of the changes in your PR

This issue fixes 2 build warnings/deprecations:

The code on these parts was relatively old (>2 years).

Description of the fixes:

• FeedFragment: Removed updateRelativeTimeViews when the activity is paused
  We don't need to call updateRelativeTimeViews when the activity is paused, because the user likely won't notice it (because it is paused).
  Despite that onResume already calls updateRelativeTimeViews so there is no need to do that twice.
• SubscriptionFragment: Simplified code and adjusted the style so that it's similar to FeedFragment
  The title there got set twice (no idea why). Simply copied use the same code (2 lines) from FeedFragment

Before/After Screenshots/Screen Record

not applicable

Fixes the following issue(s)

not applicable

APK testing

The APK can be found by going to the "Checks" tab below the title. On the left pane, click on "CI", scroll down to "artifacts" and click "app" to download the zip file which contains the debug APK of this PR.

Due diligence

• I read the contribution guidelines.

[Stypox]

Code looks good. I tested with a video in the feed published 19 minutes ago and after waiting 1 minute and switching to another app and then back to newpipe it became 20 minutes. Thanks :-)