README: update links to go.dev

[dfghjkjhgr]

Change links in the Golang repository README to link directly to go.dev, instead of golang.

Pretty much all of the links on the Golang readme go to Golang.org instead of go.dev, meaning that the website has to redirect them. Example:

Official binary distributions are available at https://golang.org/dl/.

After downloading a binary release, visit https://golang.org/doc/install for installation instructions.

This should be changed so all of the links that went to golang.org go to go.dev.

[seankhliao]

This doesn't need to be a proposal.
Feel free to file CLs directly.

[jerobado]

Hello! I'll submit a PR for this.