don't upload to docker in forked repos

Author: syphar

.github/workflows/docker.yml

@@ -20,4 +20,4 @@ jobs:
           region: us-west-1
           aws_access_key_id: "${{ secrets.aws_access_key_id }}"
           aws_secret_access_key: "${{ secrets.aws_secret_access_key }}"
-        if: github.ref == 'refs/heads/master'
+        if: ${{ github.ref == 'refs/heads/master' && github.repository_owner == 'rust-lang' }}