Update PGSQL RDS Templates

[ferricoxide]

Since initial authoring, AWS has updated available PGSQL versions. Per today's (2018-12-10) notifications, AWS is recommending updating running versions to at least 9.6.9.

AWS's currently-supported versions are (application support may vary: test if moving to a higher major):

10.4
10.3
10.1
9.6.10
9.6.9
9.6.8
9.6.6
9.6.5
9.6.3
9.6.2
9.6.1
9.5.14
9.5.13
9.5.12
9.5.10
9.5.9
9.5.7
9.5.6
9.5.4
9.5.2