github: Bump Fedora version to 39.

Fedora 37 reached EOL in November.  Switch to the most recent version
to avoid potential CI failures in the future.

Acked-by: Eelco Chaudron <echaudro@redhat.com>
Acked-by: Simon Horman <horms@ovn.org>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

.github/workflows/build-and-test.yml

@@ -307,7 +307,7 @@ jobs:
   build-linux-rpm:
     name: linux rpm fedora
     runs-on: ubuntu-latest
-    container: fedora:37
+    container: fedora:39
     timeout-minutes: 30
 
     strategy: