Auto merge of #15509 - heycam:rm-warning, r=emilio
Auto merge of #15509 - heycam:rm-warning, r=emilio

stylo: Remove useless traverse_subtree call warning.

This warning isn't useful now that we call into traverse_subtree to do the check of the dirty bits, rather than checking them up on the Gecko side.  The crashtest job is currently failing in part due to the log file exceeding 50MB because of this warning.

r? @bholley

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/15509)
<!-- Reviewable:end -->

thiagopnts/servo,mbrubeck/servo,DominoTree/servo,fiji-flo/servo,fiji-flo/servo,ConnorGBrewster/servo,SimonSapin/servo,nnethercote/servo,notriddle/servo,DominoTree/servo,pyfisch/servo,upsuper/servo,upsuper/servo,mattnenterprise/servo,jimberlage/servo,sadmansk/servo,larsbergstrom/servo,DominoTree/servo,dati91/servo,avadacatavra/servo,eddyb/servo,SimonSapin/servo,sadmansk/servo,dati91/servo,pyfisch/servo,anthgur/servo,ConnorGBrewster/servo,nnethercote/servo,anthgur/servo,dsandeephegde/servo,szeged/servo,szeged/servo,thiagopnts/servo,notriddle/servo,upsuper/servo,szeged/servo,eddyb/servo,KiChjang/servo,cbrewster/servo,thiagopnts/servo,peterjoel/servo,DominoTree/servo,mattnenterprise/servo,avadacatavra/servo,ConnorGBrewster/servo,larsbergstrom/servo,thiagopnts/servo,rnestler/servo,nnethercote/servo,sadmansk/servo,splav/servo,cbrewster/servo,upsuper/servo,saneyuki/servo,DominoTree/servo,mbrubeck/servo,dsandeephegde/servo,CJ8664/servo,mbrubeck/servo,splav/servo,dsandeephegde/servo,paulrouget/servo,nnethercote/servo,SimonSapin/servo,canaltinova/servo,CJ8664/servo,notriddle/servo,fiji-flo/servo,canaltinova/servo,saneyuki/servo,saneyuki/servo,KiChjang/servo,upsuper/servo,rnestler/servo,szeged/servo,DominoTree/servo,larsbergstrom/servo,ConnorGBrewster/servo,upsuper/servo,notriddle/servo,thiagopnts/servo,canaltinova/servo,KiChjang/servo,sadmansk/servo,rnestler/servo,mbrubeck/servo,jimberlage/servo,SimonSapin/servo,pyfisch/servo,splav/servo,SimonSapin/servo,fiji-flo/servo,notriddle/servo,splav/servo,saneyuki/servo,DominoTree/servo,mbrubeck/servo,mbrubeck/servo,pyfisch/servo,KiChjang/servo,avadacatavra/servo,szeged/servo,jimberlage/servo,eddyb/servo,peterjoel/servo,rnestler/servo,avadacatavra/servo,mattnenterprise/servo,cbrewster/servo,dati91/servo,ConnorGBrewster/servo,peterjoel/servo,emilio/servo,anthgur/servo,saneyuki/servo,larsbergstrom/servo,szeged/servo,mattnenterprise/servo,anthgur/servo,nnethercote/servo,splav/servo,rnestler/servo,notriddle/servo,SimonSapin/servo,paulrouget/servo,pyfisch/servo,KiChjang/servo,szeged/servo,emilio/servo,eddyb/servo,szeged/servo,KiChjang/servo,DominoTree/servo,dsandeephegde/servo,CJ8664/servo,emilio/servo,CJ8664/servo,dati91/servo,ConnorGBrewster/servo,nnethercote/servo,mattnenterprise/servo,anthgur/servo,splav/servo,notriddle/servo,paulrouget/servo,nnethercote/servo,anthgur/servo,pyfisch/servo,dsandeephegde/servo,paulrouget/servo,saneyuki/servo,dati91/servo,notriddle/servo,SimonSapin/servo,paulrouget/servo,paulrouget/servo,rnestler/servo,CJ8664/servo,peterjoel/servo,mattnenterprise/servo,rnestler/servo,jimberlage/servo,ConnorGBrewster/servo,paulrouget/servo,fiji-flo/servo,emilio/servo,nnethercote/servo,emilio/servo,anthgur/servo,anthgur/servo,pyfisch/servo,paulrouget/servo,thiagopnts/servo,thiagopnts/servo,nnethercote/servo,splav/servo,paulrouget/servo,peterjoel/servo,larsbergstrom/servo,fiji-flo/servo,KiChjang/servo,canaltinova/servo,canaltinova/servo,DominoTree/servo,sadmansk/servo,mattnenterprise/servo,avadacatavra/servo,rnestler/servo,larsbergstrom/servo,emilio/servo,avadacatavra/servo,avadacatavra/servo,KiChjang/servo,nnethercote/servo,larsbergstrom/servo,canaltinova/servo,eddyb/servo,fiji-flo/servo,emilio/servo,eddyb/servo,canaltinova/servo,cbrewster/servo,eddyb/servo,emilio/servo,szeged/servo,upsuper/servo,dati91/servo,CJ8664/servo,pyfisch/servo,mbrubeck/servo,jimberlage/servo,saneyuki/servo,sadmansk/servo,SimonSapin/servo,peterjoel/servo,dati91/servo,mattnenterprise/servo,CJ8664/servo,splav/servo,upsuper/servo,peterjoel/servo,dsandeephegde/servo,jimberlage/servo,peterjoel/servo,pyfisch/servo,jimberlage/servo,saneyuki/servo,cbrewster/servo,dsandeephegde/servo,cbrewster/servo,thiagopnts/servo,larsbergstrom/servo,cbrewster/servo,cbrewster/servo,peterjoel/servo,ConnorGBrewster/servo,splav/servo,splav/servo,saneyuki/servo,canaltinova/servo,saneyuki/servo,dsandeephegde/servo,peterjoel/servo,emilio/servo,notriddle/servo,KiChjang/servo,sadmansk/servo,KiChjang/servo,pyfisch/servo,szeged/servo,mbrubeck/servo,DominoTree/servo,CJ8664/servo,notriddle/servo,fiji-flo/servo,jimberlage/servo,sadmansk/servo,jimberlage/servo,paulrouget/servo,larsbergstrom/servo,eddyb/servo,emilio/servo,dati91/servo,avadacatavra/servo,larsbergstrom/servo