Rename removeBubble method to clarify it is for dismissing via drag

The removeBubble method was only used for dismissing a bubble via drag
in Launcher. Renaming the method to indicate it is only for this
purpose.
This allows us to reduce remote calls from launcher to shell when a
bubble is dismissed via drag. Otherwise we would need to make two calls,
one for removing a bubble and other for stopping the drag.
As shell keeps track of drag status in launcher for hiding the expanded
view.
Also removing the bubble key from remote call to shell to signal drag
has finished. The bubble key was not used.

Bug: 330585402
Flag: ACONFIG com.android.wm.shell.enable_bubble_bar DEVELOPMENT
Test: drag a bubble that is not expanded to dismiss target, previously
  expanded bubble should expand again
Change-Id: I57484aa3a2c0585ff7c3974d9f0d19dc1ab9dbd2