README.md: drop gstreamer repository
README.md: drop gstreamer repository

Necessary gstreamer packages are copied to qtwebkit4-backport PPA.
mbra/scudcloud,fooblahblah/scudcloud,raelgc/scudcloud,aikikode/scudcloud,zerlgi/zcswebapp,immerrr/scudcloud,sozonnyk/scudcloud,markmandel/scudcloud,christofdamian/scudcloud,christofdamian/scudcloud,sozonnyk/scudcloud,raelgc/scudcloud,zerlgi/zcswebapp,markmandel/scudcloud,garaemon/scudcloud,nicwest/scudcloud,GrandadEvans/scudcloud,GrandadEvans/scudcloud,aikikode/scudcloud,GrandadEvans/scudcloud,sozonnyk/scudcloud,markmandel/scudcloud,immerrr/scudcloud,raelgc/scudcloud,zerlgi/zcswebapp,fooblahblah/scudcloud,GrandadEvans/scudcloud,sozonnyk/scudcloud,zerlgi/zcswebapp,mbra/scudcloud,flow180/hipscud,aikikode/scudcloud,mbra/scudcloud,nicwest/scudcloud,garaemon/scudcloud,christofdamian/scudcloud,flow180/hipscud,nicwest/scudcloud,nicwest/scudcloud,mbra/scudcloud,garaemon/scudcloud,fooblahblah/scudcloud,fooblahblah/scudcloud,immerrr/scudcloud,christofdamian/scudcloud,markmandel/scudcloud,aikikode/scudcloud,flow180/hipscud,garaemon/scudcloud