Fix typo in a couple qgs docstrings (replace Arg: with Args:)

Author: kysolvik

dabench/data/_qgs.py

@@ -123,7 +123,7 @@ def rhs(self,
             ) -> np.ndarray:
         """Vector field (tendencies) of qgs system
 
-        Arg:
+        Args:
             x: State vector, shape: (system_dim)
             t: times vector. Required as argument slot for some numerical
                 integrators but unused.
@@ -142,7 +142,7 @@ def Jacobian(self,
                  ) -> np.ndarray:
         """Jacobian of the qgs system
 
-        Arg:
+        Args:
             x: State vector, shape: (system_dim)
             t: times vector. Required as argument slot for some numerical
                 integrators but unused.