ExternalIdCacheLoader: Remove unused MAX_DIFF_UPDATES constant

Change-Id: I866424c476c7a1b2f4d6ab9b8b62aa1d5ca685c7
diff --git a/java/com/google/gerrit/server/account/externalids/ExternalIdCacheLoader.java b/java/com/google/gerrit/server/account/externalids/ExternalIdCacheLoader.java
index 21bbbd2..68841da 100644
--- a/java/com/google/gerrit/server/account/externalids/ExternalIdCacheLoader.java
+++ b/java/com/google/gerrit/server/account/externalids/ExternalIdCacheLoader.java
@@ -63,9 +63,6 @@
   // Maximum number of prior states we inspect to find a base for differential. If no cached state
   // is found within this number of parents, we fall back to reading everything from scratch.
   private static final int MAX_HISTORY_LOOKBACK = 10;
-  // Maximum number of changes we perform using the differential approach. If more updates need to
-  // be applied, we fall back to reading everything from scratch.
-  private static final int MAX_DIFF_UPDATES = 50;
 
   private final ExternalIdReader externalIdReader;
   private final Provider<Cache<ObjectId, AllExternalIds>> externalIdCache;