Remove dcendents.android-maven plugin (#2277)

Summary:
This should no longer be needed as our Maven Publishing now happens
through another plugin.

This is blocking the upgrade to Gradle 7 mentioned in https://github.com/facebook/flipper/issues/2221.

It's also deprecated: https://github.com/dcendents/android-maven-gradle-plugin

Pull Request resolved: https://github.com/facebook/flipper/pull/2277

Test Plan: Manually built things, ran `uploadArchives -PdryRun=true`. No issues.

Reviewed By: mweststrate

Differential Revision: D28286834

Pulled By: passy

fbshipit-source-id: d6163e8ecf2e982cf67499861e2f387068015773

build.gradle

@@ -20,7 +20,6 @@ buildscript {
 
 plugins {
     id 'de.undercouch.download' version '4.1.1'
-    id 'com.github.dcendents.android-maven' version '2.1'
     id 'com.github.ben-manes.versions' version '0.38.0'
 }