fix: remove implementation logback-classic on gradle (woowacourse#501)

(cherry picked from commit fed02f6)

Author: geoje

study/build.gradle

@@ -19,7 +19,6 @@ repositories {
 dependencies {
     implementation 'org.springframework.boot:spring-boot-starter-web'
     implementation 'org.springframework.boot:spring-boot-starter-webflux'
-    implementation 'ch.qos.logback:logback-classic:1.5.7'
     implementation 'org.apache.commons:commons-lang3:3.14.0'
     implementation 'com.fasterxml.jackson.core:jackson-databind:2.17.1'
     implementation 'pl.allegro.tech.boot:handlebars-spring-boot-starter:0.4.1'