Fix theme(fontFamily.*) output when family contains fontFeatureSettings config

[bradlc]

This PR fixes theme(fontFamily.*) output when the font family contains fontFeatureSettings configuration:

/* Example config */
module.exports = {
  theme: {
    fontFamily: {
      sans: ['Inter', { fontFeatureSettings: '"cv11"' }],
    },
  },
}

/* Input */
.example {
  font-family: theme('fontFamily.sans');
}

/* Output before fix */
.example {
  font-family: Inter, [object Object];
}

/* Output after fix */
.example {
  font-family: Inter;
}