Fix typo in comment about topk behavior

Author: aleksraiden

tests/cppunit/types/topk_test.cc

@@ -112,7 +112,7 @@ TEST_F(RedisTopKTest, TestTopKAddAndQuery) {
   // heap is full, need remove values1.
   for (size_t i = 0; i < values2.size(); ++i) {
     bool found = false;
-    // due to decay, topk is possiable to remove values1.
+    // due to decay, topk is possible to remove values1.
     while (!found) {
       top_k_->Add(*ctx_, key_, values2[i]);
       top_k_->Query(*ctx_, key_, values2[i], &found);
@@ -133,4 +133,4 @@ TEST_F(RedisTopKTest, TestTopKAddAndQuery) {
   for (size_t i = 0; i < top_k_list.size(); ++i) {
     ASSERT_TRUE(values_set2.find(top_k_list[i]) != values_set2.end());
   }
-}
+}