ci(jscpd): add hint message for rebasing on false negatives aws#6564

## Problem
The duplicate code detection can fail when the current branch is not
rebased with the most recent version of master. This is a fairly common
false-negative. To avoid this, the PR must be kept up to date with its
target branch. However, the tool doesn't provide any hints/indication
this is the case.

## Solution
- add a hint message on failure that suggests rebasing.

Author: Hweinstock

.github/workflows/filterDuplicates.js

@@ -111,6 +111,9 @@ async function run() {
     console.log('%s duplicates found', filteredDuplicates.length)
     if (filteredDuplicates.length > 0) {
         console.log(formatDuplicates(filteredDuplicates, commitHash, repoName))
+        console.log(
+            '* Hint: if these duplicates appear unrelated to the changes, rebase onto the latest target branch.'
+        )
         process.exit(1)
     }
 }