Suppress lint warnings in leanback module.

These warnings are caused by the fact that this is a library and the
lint check doesn't see any app using the library in a TV context.

PiperOrigin-RevId: 407110725

extensions/leanback/src/main/AndroidManifest.xml

@@ -14,6 +14,8 @@
      limitations under the License.
 -->
 
-<manifest package="com.google.android.exoplayer2.ext.leanback">
+<manifest xmlns:tools="http://schemas.android.com/tools"
+  package="com.google.android.exoplayer2.ext.leanback"
+  tools:ignore="MissingLeanbackLauncher,ImpliedTouchscreenHardware,MissingLeanbackSupport">
   <uses-sdk />
 </manifest>