Update the version of Gradle, fix the compiling errors in the latest version of Android Studio (#100)

Co-authored-by: kevingpqi <[email protected]>

Author: kevingpqi123

Diff for: android/gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://mirrors.tencent.com/gradle/gradle-5.5-all.zip
+distributionUrl=https\://mirrors.tencent.com/gradle/gradle-6.9-all.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists