DOC: Change to_numeric's dtype_backend default doc (pandas-dev#59021

)

* DOC: Change `to_numic`'s `dtype_backend` default doc

* improve

* improve

* improve

pandas/core/tools/numeric.py

@@ -64,6 +64,7 @@ def to_numeric(
     ----------
     arg : scalar, list, tuple, 1-d array, or Series
         Argument to be converted.
+
     errors : {'raise', 'coerce'}, default 'raise'
         - If 'raise', then invalid parsing will raise an exception.
         - If 'coerce', then invalid parsing will be set as NaN.
@@ -88,14 +89,15 @@ def to_numeric(
         the dtype it is to be cast to, so if none of the dtypes
         checked satisfy that specification, no downcasting will be
         performed on the data.
-    dtype_backend : {'numpy_nullable', 'pyarrow'}, default 'numpy_nullable'
+
+    dtype_backend : {'numpy_nullable', 'pyarrow'}
         Back-end data type applied to the resultant :class:`DataFrame`
-        (still experimental). Behaviour is as follows:
+        (still experimental). If not specified, the default behavior
+        is to not use nullable data types. If specified, the behavior
+        is as follows:
 
-        * ``"numpy_nullable"``: returns nullable-dtype-backed :class:`DataFrame`
-          (default).
-        * ``"pyarrow"``: returns pyarrow-backed nullable :class:`ArrowDtype`
-          DataFrame.
+        * ``"numpy_nullable"``: returns with nullable-dtype-backed
+        * ``"pyarrow"``: returns with pyarrow-backed nullable :class:`ArrowDtype`
 
         .. versionadded:: 2.0