Backport PR #52399 on branch 2.0.x (DOC: Remove note about dtype_back…

…end option in convert_dtypes) (#52415)

Backport PR #52399: DOC: Remove note about dtype_backend option in convert_dtypes

Co-authored-by: Marc Garcia <garcia.marc@gmail.com>

pandas/core/generic.py

@@ -6593,13 +6593,6 @@ def convert_dtypes(
         In the future, as new dtypes are added that support ``pd.NA``, the results
         of this method will change to support those new dtypes.
 
-        .. versionadded:: 2.0
-            The nullable dtype implementation can be configured by calling
-            ``pd.set_option("mode.dtype_backend", "pandas")`` to use
-            numpy-backed nullable dtypes or
-            ``pd.set_option("mode.dtype_backend", "pyarrow")`` to use
-            pyarrow-backed nullable dtypes (using ``pd.ArrowDtype``).
-
         Examples
         --------
         >>> df = pd.DataFrame(