CI: install Julia in FormatCheck workflow so runic-action can run

`fredrikekre/runic-action@v1` (v1.4+) requires `julia` in PATH but no
longer installs it itself. Add `julia-actions/setup-julia@v2` before the
action so the format check actually runs (it has been silently passing
across many SciML repos for weeks).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>

Author: ChrisRackauckas

.github/workflows/FormatCheck.yml

@@ -14,6 +14,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6
+      - uses: julia-actions/setup-julia@v2
+        with:
+          version: '1'
       - uses: fredrikekre/runic-action@v1
         with:
           version: '1'