remove redundant reference to version switching

[heyjcollins]

It was broken also because it was an inline reference that we should have removed when we moved the version switching guide to it's own page.

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[cf-gitbot]

We have created an issue in Pivotal Tracker to manage this:

https://www.pivotaltracker.com/story/show/176099460

The labels on this github issue will be updated when the story is started.

[reidmit]

Looks good to me. Thanks @heyjcollins!