Rename alr_repos to alt_repos in branches.yaml

Signed-off-by: Barnabas Busa <busa.barnabas@gmail.com>

Author: barnabasbusa

branches.yaml

@@ -112,7 +112,7 @@ prysm:
     - fusaka-devnet-3
     - bal-devnet-0
     - block-proposal-optimisation
-  alr_repos:
+  alt_repos:
     MarcoPolo/prysm:
       - partial-columns