Change compileSdk from 30 to 31

This will allow newer libraries to be used, see #7782 and #2335. This should have no changes on the app since the targetSdk stayed the same.

app/build.gradle

@@ -8,7 +8,7 @@ plugins {
 }
 
 android {
-    compileSdk 30
+    compileSdk 31
     buildToolsVersion '30.0.3'
 
     defaultConfig {