Fix #2107 by changing notification text colour to white in night mode

[ShridharGoel]

Description (required)

Fixes #2107 Notification text should be white in night mode

Now, notification text in NotificationActivity will be white in colour when the app is in night mode.

Tests performed (required)

Tested betaDebug on API level 25.

Screenshot showing what has changed

[codecov-io]

Codecov Report

Merging #2110 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master   #2110      +/-   ##
=========================================
- Coverage     5.6%    5.6%   -0.01%     
=========================================
  Files         225     225              
  Lines       11379   11381       +2     
  Branches     1065    1066       +1     
=========================================
  Hits          638     638              
- Misses      10689   10691       +2     
  Partials       52      52

Impacted Files	Coverage Δ
...nrw/commons/notification/NotificationRenderer.java	0% <0%> (ø)	⬆️

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