Fix CI workflow to function on forked pushes.

This is what we did in the (abandoned) PR #2510 and should
have been done in PR #2512.

It means that when the CI runs on pushes
to a forked repository, it checks out that
forked repository.

.github/workflows/CI.yml

@@ -62,8 +62,6 @@ jobs:
     steps:
       - name: Checkout RMG-Py
         uses: actions/checkout@v3
-        with:
-          repository: ReactionMechanismGenerator/RMG-Py
 
       # configures the mamba environment manager and builds the environment
       - name: Setup Mambaforge Python 3.7
@@ -114,8 +112,6 @@ jobs:
     steps:
       - name: Checkout RMG-Py
         uses: actions/checkout@v3
-        with:
-          repository: ReactionMechanismGenerator/RMG-Py
 
       # configures the mamba environment manager and builds the environment
       - name: Setup Mambaforge Python 3.7