Allow let name in for-in loop in non-strict mode

[HalidOdat]

Allow let variable name in for-in loop in non-strict mode.

Fixes: https://github.com/tc39/test262/blob/72c0c5e16350a76bd41f7a1ceb7702588a2a39c6/test/language/statements/for-in/identifier-let-allowed-as-lefthandside-expression-not-strict.js

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	94,657	94,657	0
Passed	73,887	73,888	+1
Ignored	17,505	17,505	0
Failed	3,265	3,264	-1
Panics	0	0	0
Conformance	78.06%	78.06%	+0.00%

Fixed tests (1):

test/language/statements/for-in/identifier-let-allowed-as-lefthandside-expression-not-strict.js (previously Failed)

[codecov]

Codecov Report

Merging #2915 (410d990) into main (7605453) will increase coverage by 0.00%.
The diff coverage is 66.66%.

@@           Coverage Diff           @@
##             main    #2915   +/-   ##
=======================================
  Coverage   51.96%   51.96%           
=======================================
  Files         431      431           
  Lines       43657    43666    +9     
=======================================
+ Hits        22686    22691    +5     
- Misses      20971    20975    +4     

Impacted Files	Coverage Δ
...er/src/parser/statement/iteration/for_statement.rs	56.93% <66.66%> (+0.43%)	⬆️

... and 1 file with indirect coverage changes

[Razican]

Good one!