Update Chromecast's Android target SDK version to 29

Test: N/A
Bug: internal b/151449774
Change-Id: I9e66ebef8c96e9d3cf2708efdfdf95139d9d2b61
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2104663
Auto-Submit: Maxim Novikov <csbubbles@chromium.org>
Commit-Queue: Luke Halliwell (slow) <halliwell@chromium.org>
Reviewed-by: Luke Halliwell (slow) <halliwell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#750532}

chromecast/BUILD.gn

@@ -649,7 +649,7 @@ if (is_android) {
     android_manifest_dep = "//chromecast/browser/android:cast_shell_manifest"
 
     min_sdk_version = 21
-    target_sdk_version = 28
+    target_sdk_version = 29
 
     shared_libraries = [ "//chromecast/android:libcast_shell_android" ]