fix: update default k8s manifests branch version (#438)

### Description

(PR description goes here)

### Checklist

- [ ] `README.md` has been updated or is not required
- [ ] push trigger tests
- [ ] manual release test
- [ ] automated releases test
- [ ] pull request trigger tests
- [ ] schedule trigger tests
- [ ] workflow errors/warnings reviewed and addressed

### Testing done 
(for each selected checkbox, the corresponding test results link should
be listed here)

Author: mkolasinski-splunk

.github/workflows/reusable-build-test-release.yml

@@ -39,7 +39,7 @@ on:
         required: false
         description: "branch for k8s manifests to run the tests on"
         type: string
-        default: "v3.6.2"
+        default: "v3.6"
       scripted-inputs-os-list:
         required: false
         description: "list of OS used for scripted input tests"