fix: Remove obsolete deprecation warning logged on sendResponse callback calls

[rpl]

fixes #386

[codecov]

Codecov Report

Merging #406 (0f156c8) into master (032bc57) will decrease coverage by 0.32%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #406      +/-   ##
==========================================
- Coverage   91.03%   90.71%   -0.33%     
==========================================
  Files           1        1              
  Lines         145      140       -5     
==========================================
- Hits          132      127       -5     
  Misses         13       13              

Impacted Files	Coverage Δ
src/browser-polyfill.js	90.71% <ø> (-0.33%)	⬇️

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[rpl]

@Rob--W I wouldn't worry about covecov complaining about the reduced coverage, that warning wasn't explicitly covered but I guess that from codecov prespective there are just less lines of code and the same number of misses and that ends up triggering its codecov/project check failure.