[Tech] Bump org.jetbrains.kotlin.plugin.spring in /backend

Bumps [org.jetbrains.kotlin.plugin.spring](https://github.com/JetBrains/kotlin) from 1.9.22 to 1.9.23.
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v1.9.23/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.9.22...v1.9.23)

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin.plugin.spring
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

backend/build.gradle.kts

@@ -2,7 +2,7 @@ plugins {
     `java-library`
     `maven-publish`
     id("org.springframework.boot") version "3.1.7"
-    id("org.jetbrains.kotlin.plugin.spring") version "1.9.22"
+    id("org.jetbrains.kotlin.plugin.spring") version "1.9.23"
     kotlin("jvm") version "1.9.22"
     id("org.jetbrains.kotlin.plugin.allopen") version "1.9.22"
     kotlin("plugin.noarg") version "1.9.10"