Update dependency fontmake to >=3.9.0

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
fontmake	>=3.8.1 -> >=3.9.0

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Release Notes

googlei18n/fontmake (fontmake)

v3.9.0

Compare Source

• Bumped minimum depedencies:
  • fonttools >= 4.50.0
  • glyphsLib >= 6.7.0
  • ufo2ft >= 3.2.0
• The fontmake.instantiator was moved to ufo2ft.instantiator, with the same API. It's recommended that you import from the latter. The old module still works but will be removed at some point in the future.
• Fontmake can now build variable fonts with 'sparse' composite glyphs i.e. with either fewer or additional masters than their components' base glyphs, by interpolating missing sources on the fly. This works for both TTF and CFF2 variable fonts (googlefonts/glyphsLib#954).

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