Use correct primary branch

.readthedocs.yaml

@@ -18,7 +18,7 @@ build:
     # If there are no changes (git diff exits with 0) we force the command to return with 183.
     # This is a special exit code on Read the Docs that will cancel the build immediately.
     - |
-      if [ "$READTHEDOCS_VERSION_TYPE" = "external" ] && git diff --quiet origin/main -- docs/ .readthedocs.yaml requirements-initial.txt requirements.txt;
+      if [ "$READTHEDOCS_VERSION_TYPE" = "external" ] && git diff --quiet origin/6.0 -- docs/ .readthedocs.yaml requirements-initial.txt requirements.txt;
       then
         exit 183;
       fi