[Chapel Merge] Remove make spec rule

Branch: refs/heads/master
Revision: f34cad5
Author: mppf
Log Message:

Merge pull request #16533 from mppf/remove-make-spec

Remove make spec rule

It does not work since the spec now exists as .rst.
make docs will build the spec.

Reviewed by @vasslitvinov - thanks!

Modified Files:
M Makefile.devel

Compare: https://github.com/chapel-lang/chapel/compare/12aa473c97c7...f34cad5ab306