Add Maven Central Repository to buildscript to resolve build dependencies.

build.gradle

@@ -4,6 +4,7 @@ buildscript {
     classpath "org.springframework.boot:spring-boot-gradle-plugin:$springBootVersion"
   }
   repositories {
+    mavenCentral()
     gradlePluginPortal()
     maven { url 'https://repo.spring.io/plugins-release' }
   }