[DOC beta] Remove JSDoc @scope directives.

`@scope` is not a valid `YUIDoc` directive, and causes last properly
documented method/property in a file to contain the text output of any
undocumented items directly following the `@scope` directive.

Ember.Select

Before:

![screenshot](https://www.monosnap.com/image/pZCrf3m2vdqlROOUCjIuJre4a.png)

After:

![screenshot](https://www.monosnap.com/image/rfCxDtISxjm19SM85RZKbbPgK.png)

Ember.RenderBuffer

Before:
![screenshot](https://www.monosnap.com/image/ZDxRuuf9vyxMBVqIZUlghxrID.png)

After:

![screenshot](https://www.monosnap.com/image/J9eCBqdHonuB8UXC0eWQ6gQuf.png)
Merge pull request #4013 from rjackson/remove_scope_directives

[DOC beta] Remove JSDoc @scope directives.