Add dependency spring-boot-starter-webclient to docs

docs/spring-authorization-server-docs.gradle

@@ -71,6 +71,7 @@ dependencies {
 	runtimeOnly "com.h2database:h2"
 	testRuntimeOnly "org.junit.platform:junit-platform-launcher"
 	testImplementation "org.springframework.boot:spring-boot-starter-test"
+	testImplementation "org.springframework.boot:spring-boot-starter-webclient"
 	testImplementation "org.springframework.security:spring-security-test"
 	testImplementation "com.github.codemonstur:embedded-redis:1.4.3"
 }