Update RHDH main CI config to OpenShift 4.20

Updates build_root, release version, and OSD_VERSION to 4.20 for all
RHDH main branch CI jobs.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Signed-off-by: Fortune-Ndlovu <fndlovu@redhat.com>

Author: Fortune-Ndlovu

ci-operator/config/redhat-developer/rhdh/redhat-developer-rhdh-main.yaml

@@ -2,14 +2,14 @@ build_root:
   image_stream_tag:
     name: release
     namespace: openshift
-    tag: rhel-9-release-golang-1.22-openshift-4.19
+    tag: rhel-9-release-golang-1.24-openshift-4.20
   use_build_cache: true
 releases:
   latest:
     release:
       architecture: amd64
       channel: fast
-      version: "4.18"
+      version: "4.20"
 resources:
   '*':
     limits:
@@ -293,7 +293,7 @@ tests:
   steps:
     allow_skip_on_success: true
     env:
-      OSD_VERSION: 4.18.36
+      OSD_VERSION: 4.20.0
     post:
     - ref: redhat-developer-rhdh-send-data-router
     - ref: redhat-developer-rhdh-send-alert
@@ -309,7 +309,7 @@ tests:
   steps:
     allow_skip_on_success: true
     env:
-      OSD_VERSION: 4.18.36
+      OSD_VERSION: 4.20.0
     post:
     - ref: redhat-developer-rhdh-send-data-router
     - ref: redhat-developer-rhdh-send-alert