Bump AOSP version to 1.7.21

Bug: 33000560

Change-Id: I889be5dc7e9acd8a05a955bc5e11e7cd272a5aa1
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 0708afb..93b9a70 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -16,8 +16,8 @@
 
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
           package="com.android.contacts"
-          android:versionCode="10720"
-          android:versionName="1.7.20">
+          android:versionCode="10721"
+          android:versionName="1.7.21">
 
     <uses-sdk
         android:minSdkVersion="21"