_content/blog/intro-generics: fix typos in code
_content/blog/intro-generics: fix typos in code

Change-Id: I10fa17a60891c5e18a5f11895ad84dc7a5282afe
Reviewed-on: https://go-review.googlesource.com/c/website/+/395065
Run-TryBot: Eli Bendersky‎ <e83e4a9813852caf164372e4b6bd506b7819d6ab@golang.org>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@google.com>
Trust: Eli Bendersky <e83e4a9813852caf164372e4b6bd506b7819d6ab@google.com>

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