Ensure fetch-vuln-feed-data runs after clone-repository

This will hopefully fix an intermittent issue where the vuln feed zip
files disappear from the workspace before they make it to the build
step.

.tekton/scanner-pull-request.yaml

@@ -214,6 +214,7 @@ spec:
     - name: fetch-vuln-feed-data
       runAfter:
       - init
+      - clone-repository
       taskSpec:
         steps:
           - name: fetch-vuln-feed-data