[ci] Change refs to v6-38-00-patches

Similar to commit 9a30047 for v6-36-00-patches.

Author: hahnjo

.github/workflows/root-ci.yml

@@ -20,13 +20,13 @@ on:
     inputs:
       head_ref:
         type: string
-        default: master
+        default: v6-38-00-patches
       base_ref:
         type: string
-        default: master
+        default: v6-38-00-patches
       ref_name:
         type: string
-        default: master
+        default: v6-38-00-patches
 
   # Enables manual start of workflow
   workflow_dispatch:
@@ -35,12 +35,12 @@ on:
         description: rebase from ...
         type: string
         required: true
-        default: master
+        default: v6-38-00-patches
       base_ref:
         description: ... to ... (can have same value)
         type: string
         required: true
-        default: master
+        default: v6-38-00-patches
       incremental:
         description: 'Do incremental build'
         type: boolean