azure-mgmt-core shouldn't use mgmt docs build (#35936)

Author: kristapratico

eng/tox/run_sphinx_apidoc.py

@@ -25,7 +25,7 @@
 generate_mgmt_script = os.path.join(root_dir, "doc/sphinx/generate_doc.py")
 
 def is_mgmt_package(pkg_name):
-    return "mgmt"  in pkg_name or "cognitiveservices" in pkg_name
+    return pkg_name != "azure-mgmt-core" and ("mgmt" in pkg_name or "cognitiveservices" in pkg_name)
 
 def copy_existing_docs(source, target):
     for file in os.listdir(source):