DOC: fix formatting in .at docstring (pandas-dev#54730)

Author: SaraBonati

pandas/core/indexing.py

@@ -604,12 +604,12 @@ def at(self) -> _AtIndexer:
         Raises
         ------
         KeyError
-            * If getting a value and 'label' does not exist in a DataFrame or
-                Series.
+            If getting a value and 'label' does not exist in a DataFrame or Series.
+
         ValueError
-            * If row/column label pair is not a tuple or if any label from
-                the pair is not a scalar for DataFrame.
-            * If label is list-like (*excluding* NamedTuple) for Series.
+            If row/column label pair is not a tuple or if any label
+            from the pair is not a scalar for DataFrame.
+            If label is list-like (*excluding* NamedTuple) for Series.
 
         See Also
         --------