Remove [ImplementationUUID] and [InterfaceUUID] from html/canvas/*.idl

Remove [ImplementationUUID] and [InterfaceUUID] from html/canvas/*.idl
https://bugs.webkit.org/show_bug.cgi?id=77589

Reviewed by Adam Barth.

[ImplementationUUID] and [InterfaceUUID] are used in html/canvas/*.idl,
but they are not implemented in code generators and thus have no meaning.
This patch removes them.

No tests. No change in behavior.

* html/canvas/CanvasGradient.idl:
* html/canvas/CanvasPattern.idl: The file is now empty though.
* html/canvas/CanvasRenderingContext.idl:
* html/canvas/CanvasRenderingContext2D.idl:
* html/canvas/WebGLRenderingContext.idl:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@106526 268f45cc-cd09-0410-ab3c-d52691b4dbfc