glframebuffer: Remove spurious FramebufferBind
Copied from https://gitlab.freedesktop.org//gstreamer/gst-plugins-base/-/merge_requests/970
(had this branch around for a while, thought why not to submit ;-P)
This was noticed through apitrace, we endup binding the same framebuffer multiple times. Binding the framebuffer inside _attach make little sense since there might be multiple attach calls per fbo.
cc @ystreet