Use Micrometer SNAPSHOT in custom-user sample

servlet/spring-boot/java/authentication/username-password/user-details-service/custom-user/build.gradle

@@ -11,6 +11,8 @@ repositories {
 	maven { url "https://repo.spring.io/snapshot" }
 }
 
+ext["micrometer.version"] = "1.10.0-SNAPSHOT"
+
 dependencies {
 	implementation 'org.springframework.boot:spring-boot-starter-security'
 	implementation 'org.springframework.boot:spring-boot-starter-web'