OmniLib: switch to androidx

Change-Id: I0a9afd1958d194ec8afb78d12c7946c53f5f2270
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 9249b88..483aa27 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -17,9 +17,7 @@
  -->
 
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
+	  xmlns:tools="http://schemas.android.com/tools"
     package="org.omnirom.omnilib">
 
-    <uses-sdk
-        android:minSdkVersion="27" />
-
 </manifest>