Bump spring-boot-starter-data-mongodb in /plugins/gradle/example-client (#491)

Bumps [spring-boot-starter-data-mongodb](https://github.com/spring-projects/spring-boot) from 2.4.1 to 2.4.2.
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](spring-projects/spring-boot@v2.4.1...v2.4.2)

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plugins/gradle/example-client/build.gradle

@@ -14,7 +14,7 @@ mainClassName = "io.github.kobylynskyi.order.Application"
 
 dependencies {
     implementation "org.springframework.boot:spring-boot-starter-web:2.4.2"
-    implementation "org.springframework.boot:spring-boot-starter-data-mongodb:2.4.1"
+    implementation "org.springframework.boot:spring-boot-starter-data-mongodb:2.4.2"
 
     implementation "com.graphql-java-kickstart:graphql-spring-boot-starter:8.0.0"
     implementation "com.graphql-java-kickstart:graphiql-spring-boot-starter:8.0.0"