Correct async lightning-background-processor exit check docs

[TheBlueMatt]

The check to stop the background processor is true -> break, not false -> break. This simply updates the docs and leaves the code as-is.

[codecov-commenter]

Codecov Report

Base: 90.74% // Head: 90.71% // Decreases project coverage by -0.03% ⚠️

Coverage data is based on head (71739db) compared to base (3b2f694).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1843      +/-   ##
==========================================
- Coverage   90.74%   90.71%   -0.04%     
==========================================
  Files          87       87              
  Lines       47364    47364              
  Branches    47364    47364              
==========================================
- Hits        42980    42965      -15     
- Misses       4384     4399      +15     

Impacted Files	Coverage Δ
lightning-background-processor/src/lib.rs	96.23% <ø> (ø)
lightning/src/util/events.rs	38.13% <0.00%> (-0.27%)	⬇️
lightning/src/ln/functional_tests.rs	96.88% <0.00%> (-0.20%)	⬇️
lightning/src/ln/monitor_tests.rs	99.44% <0.00%> (-0.12%)	⬇️
lightning/src/ln/channelmanager.rs	85.16% <0.00%> (-0.03%)	⬇️
lightning/src/chain/channelmonitor.rs	90.70% <0.00%> (+0.05%)	⬆️

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[jkczyz]

Perhaps we should be explicit and use an enum to avoid confusion.

[TheBlueMatt]

I'm not sure we're gonna have this bug twice :). As with this case, I think a user who implements it wrong should see pretty quick that its wrong, though I agree in the future we may consider doing enums more aggressively rather than bools.