fix(renovate): drop the duplicate catalog-pin manager, the preset owns it

This repo carried its own customManager for catalog component pins. The shared preset already manages the same pins and does it correctly, so this one was redundant. It was also wrong in two ways that were actively costing us.

It lumped every component into one dependency

depNameTemplate was the fixed string gitlab-com/public-sector/pipeline, so the four pins in .gitlab-ci.yml collapsed into a single dep carrying four conflicting current versions:

pin	version
osv-verdict	v4.1.2
pages	v4.1.2
release	v4.1.2
vale	v4.1.0

That is why the open Renovate MR here is named after the group path rather than a component, and why vale sat a patch behind the other three with nothing targeting it specifically.

It stripped the leading v

gitlab\.com/gitlab-com/public-sector/pipeline/[^@]+@v?(?<currentValue>[^\s"']+)

The v? sits outside the capture group, so Renovate resolves a bare version and writes it back into a file whose include syntax requires @vX.Y.Z. This is the same defect already fixed in the preset itself: the stripped value fails confirmIfDepUpdated, the file reverts, and the branch errors out.

The preset's manager is correct

gitlab-com/public-sector/pipeline/(?<depName>[a-z][a-z0-9-]*)@(?<currentValue>v[0-9]+\.[0-9]+\.[0-9]+)

Per-component depName, and the v inside the capture group. Verified by running that regex against this repo's actual .gitlab-ci.yml: it matches all four pins individually with the prefix retained.

renovate.json is now a bare extends, which is the target shape for every repo in the estate.