[CIS-1042] Fix deleted message's appearance on channel list

[SagarSDagdu]

What does this PR do

• This PR fixes the appearance of a message in the channel list in the case where the channel's last message is a deleted one. Instead of showing the actual text of the message, we show the "Message Deleted" string.

[codecov-commenter]

Codecov Report

Merging #1318 (16bcc9f) into main (ef7eaa7) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1318   +/-   ##
=======================================
  Coverage   91.27%   91.27%           
=======================================
  Files         226      226           
  Lines        9718     9718           
=======================================
  Hits         8870     8870           
  Misses        848      848           

Flag	Coverage Δ
llc-tests	91.27% <ø> (ø)
llc-tests-ios12	91.27% <ø> (ø)

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[DominikBucher12]

💪