ci: check out loganpowell/ladybug feat/concurrent-writes for build

The Python bindings use SystemConfig::enableMultiWrites which only exists on
feat/concurrent-writes. Point the CI checkout at the fork branch so the native
module builds against the correct ladybug headers.

Author: loganpowell

.github/workflows/ci.yml

@@ -18,7 +18,8 @@ jobs:
       - name: Checkout ladybug
         uses: actions/checkout@v4
         with:
-          repository: LadybugDB/ladybug
+          repository: loganpowell/ladybug
+          ref: feat/concurrent-writes
           fetch-depth: 1
           path: ladybug