Fix RNTester Lint errors (#26279)

Summary:
Trying to build the Android RNTester app using Gradle fails with the following error:

```
  Errors found:

  [...]/RNTester/android/app/src/main/AndroidManifest.xml:2: Error: Hardware feature android.hardware.touchscreen not explicitly marked as optional  [ImpliedTouchscreenHardware]
  <manifest
   ~~~~~~~~
  [...]/RNTester/android/app/src/main/AndroidManifest.xml:2: Error: Expecting <uses-feature android:name="android.software.leanback" android:required="false" /> tag. [MissingLeanbackSupport]
  <manifest
   ~~~~~~~~
```

This PR adds the two missing `uses-feature` tags to AndroidManifest of RNTester.

## Changelog

[Android] [Fixed] - Fix RNTester Lint errors
Pull Request resolved: #26279

Test Plan: After adding the tags, the build is successful again.

Differential Revision: D17177952

Pulled By: mdvacca

fbshipit-source-id: c81dce9c6642fc8551f3d0eeb84c984ed06b18e3

Author: friederbluemle

RNTester/android/app/src/main/AndroidManifest.xml

@@ -3,6 +3,13 @@
   xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.facebook.react.uiapp">
 
+  <uses-feature
+    android:name="android.software.leanback"
+    android:required="false" />
+  <uses-feature
+    android:name="android.hardware.touchscreen"
+    android:required="false" />
+
   <uses-permission android:name="android.permission.INTERNET" />
   <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
   <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>