[Coverage][docs] for the main region array there shoudn't be a numRegionArrays : LEB128 field

[whentojump]

The docs in question are here: https://llvm.org/docs/CoverageMappingFormat.html#mapping-regions

Even in the initial commit this numRegionArrays : LEB128 field was not there

• In reader
  • The quoted starting line corresponds to expr1RHS : LEB128 earlier in docs
  • The quoted ending line corresponds to regionsForFile0 later in docs
• In writer
  • The quoted starting line corresponds to expr1RHS : LEB128 earlier in docs
  • The quoted ending line corresponds to numRegions : LEB128 later in docs
    • Note this variable is for the sub-array, not the main array
    • The first such variable is written before the loop. If there're more than one sub-arrays, later ones are written within the loop at this line

More recent code has refactored a bit (mostly in the writer) but the covmap format around this place stays the same: without this numRegionArrays : LEB128 field

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[whentojump]

@ornata @MaskRay @jroelofs please take a look. Thanks!

[whentojump]

Ping

Cc @minglotus-6: Can you please confirm this?