SceneWriter : Remove redundant `Context::Scope`
SceneWriter : Remove redundant `Context::Scope`

The `context` variable is already the current context.

andrewkaufman/gaffer,ImageEngine/gaffer,hradec/gaffer,johnhaddon/gaffer,ImageEngine/gaffer,hradec/gaffer,ImageEngine/gaffer,hradec/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,johnhaddon/gaffer,hradec/gaffer,hradec/gaffer,andrewkaufman/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,johnhaddon/gaffer,ImageEngine/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,GafferHQ/gaffer