_content/doc: fix a small typo
_content/doc: fix a small typo

it's --> its

Change-Id: Ia3d64b636704ce0108161c3c194233258c4b3d06
Reviewed-on: https://go-review.googlesource.com/c/website/+/377194
Reviewed-by: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
Run-TryBot: Emmanuel Odeke <bd234ba4276433f0e5fc7a8fa2d18274fa711567@orijtech.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: DO NOT USE <87e9c6d529889242b7e184afb632328636553ab4@google.com>

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