Fixed can_setindex for MArray

[jecs]

can_setindex now evaluates to true for Type{<:StaticArraysCore.MArray}.

See Issue 428.

@Tokazama

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (cc77c56) 70.51% compared to head (ae06bba) 70.56%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #429      +/-   ##
==========================================
+ Coverage   70.51%   70.56%   +0.05%     
==========================================
  Files           7        7              
  Lines         546      547       +1     
==========================================
+ Hits          385      386       +1     
  Misses        161      161              

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[Tokazama]

Just for the sake of completeness could you put a test in "/test/staticarrayscore.jl"? And then bump the patch version from 7.7.0 to 7.7.1 so we can release a fixed version.