_dl.sh: fix typo in expat/libmetalink/libgsasl checksums variables [ci skip]
_dl.sh: fix typo in expat/libmetalink/libgsasl checksums variables [ci skip]

libgsasl had an additional signature check, expat/libmetalink did not, but
these were added today, so the window without hash verification was short.

vszakats/harbour-deps,vszakats/harbour-deps