_content/security/vuln: remove redundant govulncheck link
_content/security/vuln: remove redundant govulncheck link

Change-Id: Ie12206dc4324c31d03949b04a5704e034e378866
Reviewed-on: https://go-review.googlesource.com/c/website/+/427878
Reviewed-by: Tatiana Bradley <ed5904c3174de8861076818d9fdd7f7c949a16e6@golang.org>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Run-TryBot: Jamal Carvalho <e0195770807aa8c82b0b128d9c0423b5ad035172@golang.org>
Auto-Submit: Jamal Carvalho <e0195770807aa8c82b0b128d9c0423b5ad035172@golang.org>
Reviewed-by: Julie Qiu <e6cb64861edcc38971590ff27c111e0e672de045@google.com>

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