Fix typo in TODO comments: MutliThreadedExecutor -> MultiThreadedExecutor (backport #2958)

[mergify]

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This is an automatic backport of pull request #2958 done by [Mergify](https://mergify.com).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.33%. Comparing base (49e1e6c) to head (4cfb434).
⚠️ Report is 1 commits behind head on jazzy.

Additional details and impacted files

@@            Coverage Diff             @@
##            jazzy    #2959      +/-   ##
==========================================
+ Coverage   89.32%   89.33%   +0.01%     
==========================================
  Files         157      157              
  Lines       18665    18664       -1     
  Branches     1492     1492              
==========================================
+ Hits        16672    16674       +2     
+ Misses       1387     1385       -2     
+ Partials      606      605       -1     

Flag	Coverage Δ
unittests	89.33% <ø> (+0.01%)	⬆️

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Files with missing lines	Coverage Δ
.../include/controller_manager/controller_manager.hpp	97.29% <ø> (ø)
controller_manager/src/controller_manager.cpp	77.19% <ø> (+0.13%)	⬆️

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