[Chromecast] Set orientation to landscape.

Set the screen orientation for CastWebContentsActivity to landscape in
the Android manifest.

Bug: internal b/74443822
Test: CQ

Change-Id: I90726b7ec7ac38f756459f246df7a3eb706f3b46
Reviewed-on: https://chromium-review.googlesource.com/963477Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Commit-Queue: Thoren Paulson <thoren@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543212}

chromecast/browser/android/apk/AndroidManifest.xml.jinja2

@@ -22,6 +22,7 @@
                   android:exported="true"
                   android:hardwareAccelerated="true"
                   android:launchMode="standard"
+                  android:screenOrientation="landscape"
                   android:taskAffinity=".CastWebContentsActivity"
                   android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection"
                   android:excludeFromRecents="true"