Revert "[Indic/GSUB] Ignore context when matching would_apply()"

This reverts commit 24dd4e56743c6ce5e01cb710ca9e01b3e527af58.

Oops.  My bad.  The change _regressed_ Malayalam test suite, not
improved it.  I'll redo it, differentiating between old-spec and
new-spec cases.
1 file changed