Remove note about Playdoh from CONTRIBUTING.md
Remove note about Playdoh from CONTRIBUTING.md

All open pull requests were submitted after the Playdoh upgrade.

davehunt/bedrock,schalkneethling/bedrock,sgarrity/bedrock,mmmavis/lightbeam-bedrock-website,pascalchevrel/bedrock,TheJJ100100/bedrock,craigcook/bedrock,pascalchevrel/bedrock,malena/bedrock,jpetto/bedrock,flodolo/bedrock,gerv/bedrock,mkmelin/bedrock,gauthierm/bedrock,ckprice/bedrock,flodolo/bedrock,hoosteeno/bedrock,alexgibson/bedrock,andreadelrio/bedrock,sylvestre/bedrock,marcoscaceres/bedrock,mermi/bedrock,craigcook/bedrock,amjadm61/bedrock,Sancus/bedrock,mkmelin/bedrock,mmmavis/lightbeam-bedrock-website,l-hedgehog/bedrock,gauthierm/bedrock,CSCI-462-01-2017/bedrock,pascalchevrel/bedrock,jpetto/bedrock,petabyte/bedrock,sylvestre/bedrock,jpetto/bedrock,CSCI-462-01-2017/bedrock,schalkneethling/bedrock,TheoChevalier/bedrock,davehunt/bedrock,mmmavis/bedrock,marcoscaceres/bedrock,petabyte/bedrock,l-hedgehog/bedrock,petabyte/bedrock,pmclanahan/bedrock,MichaelKohler/bedrock,dudepare/bedrock,MichaelKohler/bedrock,yglazko/bedrock,alexgibson/bedrock,TheoChevalier/bedrock,mozilla/bedrock,marcoscaceres/bedrock,gerv/bedrock,kyoshino/bedrock,mahinthjoe/bedrock,bensternthal/bedrock,sylvestre/bedrock,schalkneethling/bedrock,jgmize/bedrock,kyoshino/bedrock,kyoshino/bedrock,mmmavis/bedrock,TheoChevalier/bedrock,davehunt/bedrock,bensternthal/bedrock,ckprice/bedrock,flodolo/bedrock,pmclanahan/bedrock,yglazko/bedrock,jpetto/bedrock,mermi/bedrock,malena/bedrock,jacshfr/mozilla-bedrock,Jobava/bedrock,sgarrity/bedrock,SujaySKumar/bedrock,mahinthjoe/bedrock,analytics-pros/mozilla-bedrock,Jobava/bedrock,andreadelrio/bedrock,MichaelKohler/bedrock,jacshfr/mozilla-bedrock,mahinthjoe/bedrock,glogiotatidis/bedrock,Sancus/bedrock,amjadm61/bedrock,elin-moco/bedrock,pmclanahan/bedrock,hoosteeno/bedrock,craigcook/bedrock,elin-moco/bedrock,TheJJ100100/bedrock,andreadelrio/bedrock,pmclanahan/bedrock,mozilla/bedrock,l-hedgehog/bedrock,jacshfr/mozilla-bedrock,glogiotatidis/bedrock,dudepare/bedrock,mmmavis/lightbeam-bedrock-website,TheJJ100100/bedrock,hoosteeno/bedrock,rishiloyola/bedrock,ericawright/bedrock,ckprice/bedrock,marcoscaceres/bedrock,TheJJ100100/bedrock,jacshfr/mozilla-bedrock,chirilo/bedrock,analytics-pros/mozilla-bedrock,SujaySKumar/bedrock,MichaelKohler/bedrock,Jobava/bedrock,yglazko/bedrock,bensternthal/bedrock,gauthierm/bedrock,mmmavis/bedrock,sgarrity/bedrock,CSCI-462-01-2017/bedrock,mermi/bedrock,glogiotatidis/bedrock,yglazko/bedrock,flodolo/bedrock,l-hedgehog/bedrock,petabyte/bedrock,dudepare/bedrock,SujaySKumar/bedrock,CSCI-462-01-2017/bedrock,chirilo/bedrock,gerv/bedrock,mmmavis/bedrock,rishiloyola/bedrock,pascalchevrel/bedrock,amjadm61/bedrock,sgarrity/bedrock,jgmize/bedrock,gauthierm/bedrock,mkmelin/bedrock,sylvestre/bedrock,davehunt/bedrock,ericawright/bedrock,rishiloyola/bedrock,ckprice/bedrock,Sancus/bedrock,glogiotatidis/bedrock,elin-moco/bedrock,mkmelin/bedrock,kyoshino/bedrock,chirilo/bedrock,gerv/bedrock,jgmize/bedrock,andreadelrio/bedrock,alexgibson/bedrock,mozilla/bedrock,mozilla/bedrock,schalkneethling/bedrock,amjadm61/bedrock,jacshfr/mozilla-bedrock,Jobava/bedrock,ericawright/bedrock,analytics-pros/mozilla-bedrock,mermi/bedrock,hoosteeno/bedrock,amjadm61/bedrock,malena/bedrock,jgmize/bedrock,bensternthal/bedrock,TheoChevalier/bedrock,craigcook/bedrock,analytics-pros/mozilla-bedrock,chirilo/bedrock,mahinthjoe/bedrock,SujaySKumar/bedrock,malena/bedrock,elin-moco/bedrock,rishiloyola/bedrock,alexgibson/bedrock,Sancus/bedrock,ericawright/bedrock,dudepare/bedrock