Revert "Bump targetSdkVersion to 31"

Signed-off-by: Álvaro Brey <alvaro.brey@nextcloud.com>

app/build.gradle

@@ -75,7 +75,7 @@ android {
 
     defaultConfig {
         minSdkVersion 23
-        targetSdkVersion 31
+        targetSdkVersion 30
 
         buildConfigField 'boolean', 'CI', ciBuild.toString()