Bump io.ktor:ktor-serialization-kotlinx-json-jvm in /backend

Bumps [io.ktor:ktor-serialization-kotlinx-json-jvm](https://github.com/ktorio/ktor) from 2.3.3 to 2.3.8.
- [Release notes](https://github.com/ktorio/ktor/releases)
- [Changelog](https://github.com/ktorio/ktor/blob/2.3.8/CHANGELOG.md)
- [Commits](ktorio/ktor@2.3.3...2.3.8)

---
updated-dependencies:
- dependency-name: io.ktor:ktor-serialization-kotlinx-json-jvm
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

backend/build.gradle.kts

@@ -51,7 +51,7 @@ dependencies {
     api("io.ktor:ktor-client-core-jvm:2.3.6")
     api("io.ktor:ktor-client-java-jvm:2.3.3")
     api("io.ktor:ktor-client-content-negotiation-jvm:2.3.3")
-    api("io.ktor:ktor-serialization-kotlinx-json-jvm:2.3.3")
+    api("io.ktor:ktor-serialization-kotlinx-json-jvm:2.3.8")
     api("org.hibernate.validator:hibernate-validator:8.0.1.Final")
     api("jakarta.validation:jakarta.validation-api:3.0.2")
     api("com.fasterxml.jackson.module:jackson-module-kotlin:2.15.3")