fix: Fix MQTT Trigger to set ReceivedTopic

[lenny-goodell]

PR Checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

ReceivedTopic not being set by MQTT Trigger

Issue Number: #909

What is the new behavior?

ReceivedTopic now being set by MQTT Trigger

Does this PR introduce a breaking change?

• Yes
• No

Are there any new imports or modules? If so, what are they used for and why?

no

Are there any specific instructions or things that should be known prior to reviewing?

Other information

[AlexCuse]

Lgtm

[codecov-commenter]

Codecov Report

Merging #910 (9882c7d) into master (ead6592) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #910   +/-   ##
=======================================
  Coverage   63.64%   63.64%           
=======================================
  Files          33       33           
  Lines        2107     2107           
=======================================
  Hits         1341     1341           
  Misses        675      675           
  Partials       91       91           

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