fortran/95509 - fix spellcheck-operator.f90 regression

fortran/95509 - fix spellcheck-operator.f90 regression

My earlier patch to add case handling to the spell checker caused a
Fortran regression.  I believe I must have misread the test results.

This patch fixes the problem by changing the cutoff.  I chose this
value because the previous patch effectively multiplied the result of
get_edit_distance by 2 (unless a case change is involved).

gcc/fortran/ChangeLog:

	PR fortran/95509
	* misc.c (gfc_closest_fuzzy_match): Update cutoff value
	computation.