[Fix]: `helpers/callBound`: Avoid useless `$indexOf` call

[ExE-Boss]

%String.prototype.indexOf% returns ‑1 when the substring wasn’t found, and ToBoolean(‑1) returns true, so the correct check should’ve been $indexOf(name, '.prototype.') > 0, but doing that now would break many things, including PromiseResolve.

The only case where callBound could return the same function object as GetIntrinsic would’ve been callBound('.prototype.something') ^{(callBound('%.prototype.something%') would return the result of callBind, as the index of '.prototype.' is 1),} but that would cause GetIntrinsic to throw a SyntaxError.

[codecov[bot]]

Codecov Report

Merging #108 into master will decrease coverage by 0.00%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #108      +/-   ##
==========================================
- Coverage   90.85%   90.85%   -0.01%     
==========================================
  Files         682      682              
  Lines        9422     9421       -1     
  Branches     2169     2169              
==========================================
- Hits         8560     8559       -1     
  Misses        862      862              

Impacted Files	Coverage Δ
helpers/callBound.js	100.00% <100.00%> (ø)

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[ljharb]

callBound has been extracted to https://github.com/ljharb/call-bind; any further improvements should go there. Thanks!