chore(deps): bump org.camunda.bpm:camunda-bom in /platform

Bumps org.camunda.bpm:camunda-bom from 7.20.0 to 7.21.0.

---
updated-dependencies:
- dependency-name: org.camunda.bpm:camunda-bom
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

platform/pom.xml

@@ -21,7 +21,7 @@
         <lombok.version>1.18.32</lombok.version>
         <lombok.mapstruct.binding.version>0.2.0</lombok.mapstruct.binding.version>
         <org.mapstruct.version>1.5.5.Final</org.mapstruct.version>
-        <camunda7.version>7.20.0</camunda7.version>
+        <camunda7.version>7.21.0</camunda7.version>
         <camunda8.version>8.4.0</camunda8.version>
         <springdoc-openapi.version>2.5.0</springdoc-openapi.version>
         <kotlin.version>1.9.24</kotlin.version>