Change isokinetic_integrator generation API (#689)

Author: junpenglao

blackjax/mcmc/integrators.py

@@ -374,9 +374,8 @@ def format_isokinetic_state_output(
 
 def generate_isokinetic_integrator(coefficients):
     def isokinetic_integrator(
-        logdensity_fn: Callable, *args, **kwargs
+        logdensity_fn: Callable, sqrt_diag_cov: ArrayTree = 1.0
     ) -> GeneralIntegrator:
-        sqrt_diag_cov = kwargs.get("sqrt_diag_cov", 1.0)
         position_update_fn = euclidean_position_update_fn(logdensity_fn)
         one_step = generalized_two_stage_integrator(
             esh_dynamics_momentum_update_one_step(sqrt_diag_cov),