fix small typo in comment

googletest/samples/sample3_unittest.cc

@@ -72,7 +72,7 @@ class QueueTest : public testing::Test {
              // accessed from sub-classes.
 
   // virtual void SetUp() will be called before each test is run.  You
-  // should define it if you need to initialize the varaibles.
+  // should define it if you need to initialize the variables.
   // Otherwise, this can be skipped.
   virtual void SetUp() {
     q1_.Enqueue(1);