Revert "widget: Install default CSS at FALLBACK priority"
Revert "widget: Install default CSS at FALLBACK priority"

This causes a off-by-one error somewhere that makes sizing not work correctly
anymore. So revert this for now.

This reverts commit 8d970eaf129221d925a26f4423b4baf4524ff481.

saitoha/vte-sixel,rvu95/vte,rvu95/vte,thestinger/vte-ng,rvu95/vte,flaxandteal/gasket-vte,flaxandteal/gasket-vte,jessevdk/vte,jessevdk/vte,thestinger/vte-ng,rvu95/vte,flaxandteal/gasket-vte,thestinger/vte-ng,flaxandteal/gasket-vte,jessevdk/vte,saitoha/vte-sixel,saitoha/vte-sixel,jessevdk/vte