Docs: Remove CI for gh-pages, use googleapis.dev for api_core refs. (#9085)

Author: busunkim96

docs/conf.py

@@ -340,10 +340,7 @@
 intersphinx_mapping = {
     "python": ("http://python.readthedocs.org/en/latest/", None),
     "google-auth": ("https://google-auth.readthedocs.io/en/stable", None),
-    "google.api_core": (
-        "https://googleapis.github.io/google-cloud-python/latest",
-        None,
-    ),
+    "google.api_core": ("https://googleapis.dev/python/google-api-core/latest", None),
     "grpc": ("https://grpc.io/grpc/python/", None),
     "requests": ("https://2.python-requests.org/en/master/", None),
 }