Use CATransaction to set completion block in changeInputContentBottomMarginTo

[leonspok]

I found that completion block from UIView.animate is not called if animation is started after interactive pop gesture begins. Using CATransaction's completion block fixes the issue.

[codecov-io]

Codecov Report

Merging #599 into master will decrease coverage by 0.05%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master     #599      +/-   ##
==========================================
- Coverage   57.97%   57.91%   -0.06%     
==========================================
  Files          91       91              
  Lines        3879     3883       +4     
==========================================
  Hits         2249     2249              
- Misses       1630     1634       +4

Impacted Files	Coverage Δ
...Source/ChatController/BaseChatViewController.swift	67.98% <0%> (-1%)	⬇️

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