fix: Remove tiled writer if submitted task doesn't exist

[tpoliaw]

Whenever a task is submitted, a TiledWriter is added to the run engine
and is only removed when the task is complete. If the task never starts
due to not being found, the writer would never be removed and subsequent
tasks would have duplicate writers causing write errors to tiled.

Catching the KeyError and removing the subscribers immediately is a
workaround that works but should be removed when the internal pending
tasks queue is removed.

Fixes #1480

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.09%. Comparing base (774781b) to head (0c1ffa8).

Files with missing lines	Patch %	Lines
src/blueapi/service/interface.py	33.33%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1484      +/-   ##
==========================================
- Coverage   95.21%   95.09%   -0.12%     
==========================================
  Files          43       43              
  Lines        3132     3137       +5     
==========================================
+ Hits         2982     2983       +1     
- Misses        150      154       +4     

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