tc GoDoc starts with sentence about the enum package

[zrhoffman]

I'm submitting a ...

• bug report
• new feature / enhancement request
• improvement request (usability, performance, tech debt, etc.)
• other

Traffic Control components affected ...

• CDN in a Box
• Documentation
• Grove
• Traffic Control Client
• Traffic Monitor
• Traffic Ops
• Traffic Ops ORT
• Traffic Portal
• Traffic Router
• Traffic Stats
• Traffic Vault
• unknown

Current behavior:

If you visit https://godoc.org/github.com/apache/trafficcontrol/lib/go-tc, the GoDoc for the tc package will start with the following sentence:

Package enum contains enumerations and strongly typed names.

Expected / new behavior:

The tc GoDoc should only describe itself as the tc package.

Minimal reproduction of the problem with instructions:

1. Run these commands:

   go get -u golang.org/x/tools/cmd/godoc
   godoc -http=:6060

2. In your browser, navigate to http://localhost:6060/pkg/github.com/apache/trafficcontrol/lib/go-tc/

3. Check the first sentence of the Overview section

Anything else:

enum.go should remain part of the tc package. See #4293 (comment) for discussion.