Avoid printing "reason unknown" for extract entries

This was happening when the main Gradle User Home entry was not saved due to
having an unchanged cache key.

Fixes #309

src/cache-extract-entries.ts

@@ -213,7 +213,7 @@ abstract class AbstractEntryExtractor {
 
         if (previouslyRestoredKey === cacheKey) {
             cacheDebug(`No change to previously restored ${artifactType}. Not saving.`)
-            entryListener.markUnchanged('contents unchanged')
+            entryListener.markUnsaved('contents unchanged')
         } else {
             core.info(`Caching ${artifactType} with path '${pattern}' and cache key: ${cacheKey}`)
             await saveCache([pattern], cacheKey, entryListener)