fix: remove stale Sparkle monotonic guard broken by run-ID build numbers

Since the single-lane collapse, every ship (auto-ship and milestone tag)
derives its Sparkle build number from the GitHub run ID; the committed
CURRENT_PROJECT_VERSION is a local-dev default that is intentionally
never shipped (documented in release.yml). The first auto-ship published
build 2890114033301, so this guard — which compares the committed value
(83) against the published appcast — now fails permanently on every CI
run and blocks all PRs.

The invariant it protected (never ship a build number <= the published
one) is still enforced at the right place: release.yml's runtime
monotonic guard checks the EFFECTIVE build against the appcast before
publishing.

Author: arzafran

.github/workflows/ci.yml

@@ -38,9 +38,6 @@ jobs:
       - name: Validate current GhosttyKit checksum pin
         run: ./tests/test_ci_ghosttykit_checksum_present.sh
 
-      - name: Validate Sparkle build number is monotonic
-        run: ./tests/test_ci_sparkle_build_monotonic.sh
-
   remote-daemon-tests:
     runs-on: ubuntu-latest
     steps: