docs: update instructions

Author: shuoweil

bigframes/series.py

@@ -321,7 +321,7 @@ def blob(self) -> blob.BlobAccessor:
         Accessor for Blob operations.
         """
         warnings.warn(
-            "The blob accessor is deprecated and will be removed in a future release.",
+            "The blob accessor is deprecated and will be removed in a future release. Use bigframes.bigquery.obj functions instead.",
             category=bfe.ApiDeprecationWarning,
             stacklevel=2,
         )

bigframes/session/__init__.py

@@ -2292,7 +2292,7 @@ def read_gbq_object_table(
                 Result BigFrames DataFrame.
         """
         warnings.warn(
-            "read_gbq_object_table is deprecated and will be removed in a future release.",
+            "read_gbq_object_table is deprecated and will be removed in a future release. Use read_gbq with 'ref' column instead.",
             category=bfe.ApiDeprecationWarning,
             stacklevel=2,
         )