ci: pin valk-guard to v0.1.2

Author: eitamring

.github/workflows/valk-guard.yml

@@ -9,7 +9,7 @@ permissions:
   pull-requests: write
 
 env:
-  VALK_GUARD_INSTALL_REF: ad976e64f23b230bec5af33efeb56c04708e445f
+  VALK_GUARD_INSTALL_REF: v0.1.2
 
 jobs:
   scan: