PostgreSQL requirements table: GitLab 17 will require PG14

What does this MR do?

Adds PostgreSQL minimum for GitLab 17.

Change follows from the a discussion in the deprecation MR for PostgreSQL 13.

Why 14.7?

Since we usually specify a patch release, I looked to see if I could find out what groupdistribution was planning to ship initially in 16.x. The draft MR specifies 14.7.

We do need to specify a healthy minimum patch level since:

The new PostgreSQL 14.4 release fixes an issue with all versions of PostgreSQL 14 that can lead to silent corruption of indexes.

But for sure, if we later revise this upwards or find out about relevant bugs in PostgreSQL 14 this should be jacked up to a later patch level.

Related issues

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