docs: Update minimum Postgres supported version

Author: Dan-Heath

content/boundary/v0.20.x/content/docs/enterprise/supported-versions.mdx

@@ -58,5 +58,5 @@ To view the Desktop version along with the corresponding CLI and control plane v
 
 ## PostgreSQL support policy
 
-Boundary Enterprise will only support PostgreSQL version 13 and above at launch.
+Boundary Enterprise supports PostgreSQL versions 16 and above.
 On an ongoing basis, Boundary will end support for a PostgreSQL version one (1) year prior to its EOL as documented on PostgreSQL’s versioning policy website.