Bump the java-production-dependencies group in /backend with 2 updates

Bumps the java-production-dependencies group in /backend with 2 updates: [io.quarkus:quarkus-universe-bom](https://github.com/quarkusio/quarkus-platform) and io.quarkus:quarkus-maven-plugin.


Updates `io.quarkus:quarkus-universe-bom` from 3.8.2 to 3.8.4
- [Commits](quarkusio/quarkus-platform@3.8.2...3.8.4)

Updates `io.quarkus:quarkus-maven-plugin` from 3.8.2 to 3.8.4

Updates `io.quarkus:quarkus-maven-plugin` from 3.8.2 to 3.8.4

---
updated-dependencies:
- dependency-name: io.quarkus:quarkus-universe-bom
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: java-production-dependencies
- dependency-name: io.quarkus:quarkus-maven-plugin
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: java-production-dependencies
- dependency-name: io.quarkus:quarkus-maven-plugin
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: java-production-dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>

backend/pom.xml

@@ -12,7 +12,7 @@
     <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
     <quarkus.container-image.group>cryptomator</quarkus.container-image.group>
     <quarkus.container-image.name>hub</quarkus.container-image.name>
-    <quarkus.platform.version>3.8.2</quarkus.platform.version>
+    <quarkus.platform.version>3.8.4</quarkus.platform.version>
     <quarkus.jib.base-jvm-image>eclipse-temurin:21-jre</quarkus.jib.base-jvm-image> <!-- irrelevant for -Pnative -->
     <jwt.version>4.4.0</jwt.version>
     <compiler-plugin.version>3.13.0</compiler-plugin.version>