• [featureVars] Update OS/2.usMaxContext if possible after addFeatureVariationsRaw (#3894).
• [vhmtx] raise TTLibError('not enough data...') when hmtx/vmtx are truncated (#3843, #3901).
• [feaLib] Combine duplicate features that have the same set of lookups regardless of the order in which those lookups are added to the feature (#3895).
• [varLib] Deprecate varLib.mutator in favor of varLib.instancer. The latter provides equivalent full (static font) instancing in addition to partial VF instancing.
  CLI users should replace fonttools varLib.mutator with fonttools varLib.instancer. API users should migrate to fontTools.varLib.instancer.instantiateVariableFont (#2680).