ci: temporarily disable template builds (#16371)

# Overview

Template build CI jobs fail on `main` after the version bump to
`4.0.0-beta.0` because
`tools/scripts/src/build-template-with-local-pkgs.ts` hardcodes a stale
placeholder version (`3.42.0`) when rewriting `workspace:*` deps, and
the 4.x beta isn't published on npm yet. Disable the jobs until the next
4.x beta ships.

Example failure:
https://github.com/payloadcms/payload/actions/runs/24848623266/job/72743812553

## Key Changes

- **Skip `build-and-test-templates` in `main.yml`**
- Set the job's `if:` to `false` with a comment noting it's temporary
and should be re-enabled after the next 4.x beta publishes.
- Skipped jobs report `skipped`, so the `all-green` gate (which only
fails on `failure`/`cancelled`) still passes.

## Design Decisions

Chose to gate at the workflow level rather than patch the template build
script. The underlying fix (reading the real workspace version instead
of the hardcoded `3.42.0`) belongs in a follow-up once we can validate
against a published beta; short-circuiting the job here unblocks `main`
without masking the problem in the script itself.

Author: denolfe

.github/workflows/main.yml

@@ -374,7 +374,9 @@ jobs:
   build-and-test-templates:
     runs-on: ubuntu-24.04
     needs: [changes, build]
-    if: needs.changes.outputs.needs_build == 'true'
+    # Temporarily disabled: template builds require a published beta of workspace packages.
+    # Re-enable once the next 4.x beta is published on npm.
+    if: false
     name: build-template-${{ matrix.template }}-${{ matrix.database }}
     strategy:
       fail-fast: false