style: Removed layout.css.all-shorthand.enabled pref.
style: Removed layout.css.all-shorthand.enabled pref.

The 'all' shorthand has shipped a long time ago, so this pref is not needed
anymore.

Bug: 1459524
Reviewed-by: heycam
MozReview-Commit-ID: GND8qSVAfCG

KiChjang/servo,nnethercote/servo,larsbergstrom/servo,emilio/servo,sadmansk/servo,splav/servo,larsbergstrom/servo,paulrouget/servo,DominoTree/servo,emilio/servo,SimonSapin/servo,nnethercote/servo,KiChjang/servo,jimberlage/servo,cbrewster/servo,emilio/servo,nnethercote/servo,dati91/servo,paulrouget/servo,jimberlage/servo,dati91/servo,SimonSapin/servo,splav/servo,ConnorGBrewster/servo,peterjoel/servo,cbrewster/servo,larsbergstrom/servo,SimonSapin/servo,larsbergstrom/servo,nnethercote/servo,splav/servo,peterjoel/servo,dati91/servo,saneyuki/servo,paulrouget/servo,saneyuki/servo,jimberlage/servo,peterjoel/servo,peterjoel/servo,splav/servo,szeged/servo,ConnorGBrewster/servo,sadmansk/servo,saneyuki/servo,ConnorGBrewster/servo,notriddle/servo,dati91/servo,jimberlage/servo,pyfisch/servo,jimberlage/servo,cbrewster/servo,szeged/servo,ConnorGBrewster/servo,dati91/servo,nnethercote/servo,KiChjang/servo,pyfisch/servo,peterjoel/servo,paulrouget/servo,szeged/servo,szeged/servo,KiChjang/servo,peterjoel/servo,nnethercote/servo,saneyuki/servo,SimonSapin/servo,pyfisch/servo,notriddle/servo,KiChjang/servo,pyfisch/servo,splav/servo,notriddle/servo,emilio/servo,paulrouget/servo,nnethercote/servo,DominoTree/servo,emilio/servo,pyfisch/servo,DominoTree/servo,saneyuki/servo,sadmansk/servo,dati91/servo,szeged/servo,paulrouget/servo,DominoTree/servo,szeged/servo,paulrouget/servo,saneyuki/servo,pyfisch/servo,szeged/servo,larsbergstrom/servo,emilio/servo,saneyuki/servo,paulrouget/servo,sadmansk/servo,larsbergstrom/servo,SimonSapin/servo,emilio/servo,SimonSapin/servo,DominoTree/servo,larsbergstrom/servo,notriddle/servo,ConnorGBrewster/servo,saneyuki/servo,szeged/servo,notriddle/servo,ConnorGBrewster/servo,notriddle/servo,emilio/servo,jimberlage/servo,larsbergstrom/servo,ConnorGBrewster/servo,pyfisch/servo,peterjoel/servo,nnethercote/servo,pyfisch/servo,splav/servo,emilio/servo,saneyuki/servo,szeged/servo,SimonSapin/servo,larsbergstrom/servo,sadmansk/servo,nnethercote/servo,sadmansk/servo,pyfisch/servo,sadmansk/servo,sadmansk/servo,jimberlage/servo,peterjoel/servo,splav/servo,peterjoel/servo,cbrewster/servo,KiChjang/servo,DominoTree/servo,jimberlage/servo,splav/servo,notriddle/servo,KiChjang/servo,SimonSapin/servo,saneyuki/servo,pyfisch/servo,szeged/servo,cbrewster/servo,peterjoel/servo,nnethercote/servo,emilio/servo,cbrewster/servo,dati91/servo,cbrewster/servo,KiChjang/servo,KiChjang/servo,DominoTree/servo,KiChjang/servo,paulrouget/servo,ConnorGBrewster/servo,notriddle/servo,notriddle/servo,DominoTree/servo,cbrewster/servo,DominoTree/servo,larsbergstrom/servo,DominoTree/servo,paulrouget/servo,jimberlage/servo,dati91/servo,splav/servo,splav/servo,notriddle/servo