ci: test Snyk scan

Author: faucomte97

.github/workflows/main.yaml

@@ -7,5 +7,5 @@ on:
 
 jobs:
   main:
-    uses: ocadotechnology/codeforlife-workspace/.github/workflows/backend.yaml@main
+    uses: ocadotechnology/codeforlife-workspace/.github/workflows/backend.yaml@snyk
     secrets: inherit