Delete unused TagSet.weigh method

I added this during the Guava cache changes, thinking we would
weigh the elements of the TagCache, but I aborted that idea and
didn't quite clean up all of the code.

Change-Id: I329db9f0c78dc51172422ba7463137edbb7c6e15

gerrit-server/src/main/java/com/google/gerrit/server/git/TagSet.java

@@ -58,15 +58,6 @@ class TagSet {
     return tags.get(id);
   }
 
-  int weigh() {
-    int refCnt = refs.size();
-    int bits = refCnt / 8;
-    int size = 16 + 3*8 + 16 + 16;
-    size += (16 + 16 + 8+ 4 + 36 + 120) * refCnt;
-    size += (16 + 36 + 16 + bits) * tags.size();
-    return size;
-  }
-
   void updateFastForward(String refName, ObjectId oldValue,
       ObjectId newValue) {
     CachedRef ref = refs.get(refName);