Fix order of notifications

[maskaravivek]

Description

Part of fixes for #7. Now the newest notification is on the top.

Screenshots showing what changed

Before

After

[codecov-io]

Codecov Report

Merging #1184 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master   #1184      +/-   ##
=========================================
- Coverage    3.82%   3.82%   -0.01%     
=========================================
  Files         125     125              
  Lines        5798    5799       +1     
  Branches      568     568              
=========================================
  Hits          222     222              
- Misses       5561    5562       +1     
  Partials       15      15

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

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