fix: always include m.mentions on outgoing messages

[kamor-famedly]

Closes #2302

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.77%. Comparing base (f10161c) to head (62c6d4d).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2330      +/-   ##
==========================================
+ Coverage   55.32%   55.77%   +0.45%     
==========================================
  Files         160      160              
  Lines       19854    19868      +14     
==========================================
+ Hits        10984    11082      +98     
+ Misses       8870     8786      -84     

Files with missing lines	Coverage Δ
lib/src/room.dart	76.32% <100.00%> (+0.06%)	⬆️
lib/src/utils/commands_extension.dart	65.21% <100.00%> (+0.38%)	⬆️
lib/src/utils/pushrule_evaluator.dart	96.70% <100.00%> (+0.15%)	⬆️

... and 14 files with indirect coverage changes

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