Remove vestigial *.SH code which can link the extracted file into ../

Remove vestigial *.SH code which can link the extracted file into ../

4 of the *.SH files have code which links the extracted file into the parent
directory if the current directory ends SH. This code dates from Perl 1.
It seems that the intent was that the *.SH files could live in a SH/
directory, but that feature was neither used or mentioned in the
documentation in Perl 1, and hasn't been used since.