BLD: make containers only build on bilby-dev (#1058)

I've seen emails from build jobs failing on forks, we should just builds everywhere except bilby-dev/bilby.

This change will mean that if we want to build from an unmerged branch, we will need that branch to be pushed to bilby-dev.

Author: ColmTalbot

.github/workflows/build-containers.yml

@@ -7,6 +7,7 @@ on:
 
 jobs:
   build-container:
+    if: ${{ github.repository == 'bilby-dev/bilby' }}
     permissions:
       attestations: write
       contents: read