android: fix gradle warning

android/app/build.gradle

 
         android.applicationVariants.all { variant ->
             variant.outputs.each { output ->
-                output.processManifest.doLast {
+                output.getProcessManifestProvider().get().doLast {
                     def outputDir = manifestOutputDirectory.get().asFile
                     def manifestPath = new File(outputDir, 'AndroidManifest.xml')
                     def charset = 'UTF-8'