build: update version

Change-Id: I43f4a09cc579dd01c4fb0b0ad9410b5fb8bbd690

ring-android/app/build.gradle

@@ -9,8 +9,8 @@ android {
     defaultConfig {
         minSdkVersion 21
         targetSdkVersion 30
-        versionCode 299
-        versionName "20210517-01"
+        versionCode 301
+        versionName "20210521-01"
     }
     sourceSets {
         main {

ring-android/build.gradle

@@ -5,7 +5,7 @@ buildscript {
         mavenCentral()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:4.2.0'
+        classpath 'com.android.tools.build:gradle:4.2.1'
         classpath 'com.google.gms:google-services:4.3.5'
     }
 }