Rename matcher `ContainsKey` to `Contains`.

Signed-off-by: Eric Paniagua <epaniagua@google.com>

testing/common/matchers.h

@@ -26,7 +26,7 @@
 namespace kaleidoscope {
 namespace testing {
 
-auto ContainsKey(Key key) { return ::testing::Contains(key.getKeyCode()); }
+auto Contains(Key key) { return ::testing::Contains(key.getKeyCode()); }
 
 }  // namespace testing
 }  // namespace kaleidoscope

testing/kaleidoscope/test/simulator_test.cpp

@@ -44,7 +44,7 @@ TEST_F(KeyboardReports, KeysActiveWhenPressed) {
   ASSERT_EQ(state->KeyboardReports().size(), 1);
   EXPECT_THAT(
       state->KeyboardReports(0).ActiveKeycodes(),
-      ContainsKey(Key_A));
+      Contains(Key_A));
 
   sim_.Release(2, 1);  // A
   state = RunCycle();