Revert "TEMP: Add _repr_html_ for Colab widget display fix"

This reverts commit a183d52.

Author: shuoweil

bigframes/dataframe.py

@@ -947,17 +947,6 @@ def _repr_mimebundle_(self, include=None, exclude=None):
 
         return {"text/html": html_string, "text/plain": text_representation}
 
-    def _repr_html_(self):
-        """
-        Renders the DataFrame as HTML.
-        This method is used by IPython to display the DataFrame.
-        """
-        # If in anywidget mode, return None to defer to _repr_mimebundle_
-        # which will provide the richer anywidget representation.
-        if bigframes.options.display.repr_mode == "anywidget":
-            return None
-        return self._repr_mimebundle_()["text/html"]
-
     def _create_html_representation(
         self,
         pandas_df: pandas.DataFrame,