Use the lithium_rebase branch of RMG-database for CI

This is needed for testing.
Once lithium_rebase is merged to main on the database,
we can go back to using main.

Author: ssun30

.github/workflows/CI.yml

@@ -47,7 +47,7 @@ concurrency:
 env:
   # if running on RMG-Py but requiring changes on an un-merged branch of RMG-database, replace
   # main with the name of the branch
-  RMG_DATABASE_BRANCH: main
+  RMG_DATABASE_BRANCH: lithium_rebase
 
 
 jobs: