Update fdbserver/SkipList.cpp

Co-Authored-By: A.J. Beamon <ajbeamon@users.noreply.github.com>

fdbserver/SkipList.cpp

@@ -1052,7 +1052,7 @@ class MiniConflictSet : NonCopyable {
 	}
 	wordType highBits(int b){ // bits (b&bucketMask) and higher are 1
 		#pragma warning(disable: 4146)
-		return -(wordType(1) << (b & bucketMask));
+		return -bitMask(b);
 		#pragma warning(default: 4146)
 	}
 	wordType lowBits(int b) { // bits lower than (b&bucketMask) are 1