[PF-2983]: Bump io.kubernetes:client-java from 20.0.1 to 21.0.1-legacy

Bumps [io.kubernetes:client-java](https://github.com/kubernetes-client/java) from 20.0.1 to 21.0.1-legacy.
- [Release notes](https://github.com/kubernetes-client/java/releases)
- [Changelog](https://github.com/kubernetes-client/java/blob/master/CHANGELOG.md)
- [Commits](https://github.com/kubernetes-client/java/commits)

---
updated-dependencies:
- dependency-name: io.kubernetes:client-java
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

build.gradle

@@ -56,7 +56,7 @@ dependencies {
     annotationProcessor group: 'org.springframework.boot', name: 'spring-boot-configuration-processor'
 
     // Misc. Services
-    implementation group: 'io.kubernetes', name: 'client-java', version: '20.0.1'
+    implementation group: 'io.kubernetes', name: 'client-java', version: '21.0.1-legacy'
     constraints {
         implementation('org.bouncycastle:bcprov-jdk18on:1.78.1') {
             because 'https://broadworkbench.atlassian.net/browse/DCJ-275'