tour: correct typo
tour: correct typo

Change-Id: I14f0317c1f6c36aa922c43eab45a7bc4dd698142
Reviewed-on: https://go-review.googlesource.com/c/website/+/394314
Reviewed-by: Eli Bendersky‎ <e83e4a9813852caf164372e4b6bd506b7819d6ab@golang.org>
Reviewed-by: Cherry Mui <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
Run-TryBot: Eli Bendersky‎ <e83e4a9813852caf164372e4b6bd506b7819d6ab@golang.org>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Trust: Eli Bendersky <e83e4a9813852caf164372e4b6bd506b7819d6ab@google.com>

golang/website,golang/website,golang/website,golang/website,golang/website,golang/website,golang/website