update gradle plugin

@@ -11,7 +11,7 @@ buildscript {
 
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:7.0.0-alpha14'
+        classpath 'com.android.tools.build:gradle:7.0.0-alpha15'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
         classpath "org.jetbrains.kotlin:kotlin-serialization:$kotlin_version"
         classpath "org.jetbrains.dokka:dokka-gradle-plugin:$dokka_version"

 #Thu Apr 29 14:50:17 JST 2021
 distributionBase=GRADLE_USER_HOME
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.0-rc-1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.0-bin.zip
 distributionPath=wrapper/dists
 zipStorePath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME