Update fonttools and ufo2ft in requirements.txt

[anthrotype]

This should give us more 'greens' on the fontc crater, in particular:

notable changes in ufo2ft 3.7.3:

• Fix empty public.postscriptNames triggering uniXXXX derivation (Fix empty public.postscriptNames dict incorrectly triggering uniXXXX derivation ufo2ft#980).

And in fonttools 4.63

• [cu2qu] Fix Cython complex-division rounding difference in split_cubic_into_three that could cause ±1 off-curve coordinate shifts (Different number of points in outline in variable font vs if static fonttools/fonttools#3928, [cu2qu] Use _complex_div_by_real in split_cubic_into_three fonttools/fonttools#4083).
• [designspaceLib] Fix map_backward for many-to-one (flat-segment) axis maps that silently dropped entries via dict comprehension (SUSE-Italic GPOS kerning variation region mismatch ufo2ft#978, [designspaceLib] Fix map_backward for many-to-one axis maps fonttools/fonttools#4085).

JMM