Docs for Sidenav needs update

[bogacg]

Bug, feature request, or proposal:

Bug

What is the expected behavior?

Having Docs that reflect latest updates in project:

Example in Docs for Sidenav being compatible with latest version (2.0.0-beta.10). There is now Drawer Component.
Material 2.0.0-beta.10 produces .mat-drawer-content class for content of Sidenav. Drawer component's content seems to handle scrolling case as well, so example does not need to add overflow: auto;

What is the current behavior?

Having examples of older version.

.mat-sidenav-content class is referred in current Docs example, also scrolling is handled in that example, which is not needed with current version (for content at least, if not sidenav).

[willshowell]

Can be closed via #7099

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