Remove nightly run of Postgres 14

[OriolMunoz-da]

Do once we've switched everything to Postgres 17
See here: https://github.com/hyperledger-labs/splice/pull/1313/changes#diff-91052a04880c36afc9fcda2d4b15beaee5d65f99e596c9729d32cf6702ecb282R1

[meiersi-da]

@OriolMunoz-da : what's our strategy wrt rolling out the Pg upgrade to our clusters? How will the other SV operators roll out that change? and be informed ahead of time of that change?

[OriolMunoz-da]

@meiersi-da see #1129 (comment)