_content/security/vuln: fix typo and broken links in database.md
_content/security/vuln: fix typo and broken links in database.md

Change-Id: I8eb859e87a082620c832d4f35ac422163a4d3cfe
Reviewed-on: https://go-review.googlesource.com/c/website/+/427599
Reviewed-by: Tatiana Bradley <ed5904c3174de8861076818d9fdd7f7c949a16e6@golang.org>
Reviewed-by: Brandon Kessler <ca053a7d85137b77c1c549ec7c63bd3f6ad3fa72@google.com>

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