Update grammar of documentation

Author: dazza5000

runner/AndroidJunitRunnerSample/app/src/androidTest/java/com/example/android/testing/androidjunitrunnersample/CalculatorAddParameterizedTest.java

@@ -35,7 +35,7 @@
 /**
  * JUnit4 tests for the calculator's add logic.
  *
- * <p> This test uses a Junit4s Parameterized tests features which uses annotations to pass
+ * <p> This test uses Junit4s Parameterized tests features which uses annotations to pass
  * parameters into a unit test. The way this works is that you have to use the {@link Parameterized}
  * runner to run your tests.
  * </p>
@@ -91,4 +91,4 @@ public void testAdd_TwoNumbers() {
         assertThat(resultAdd, is(equalTo(mExpectedResult)));
     }
 
-}
+}