TST: update density doctest for new pressure_ISA discretization

The finer spline knots shift density at 1000 m by ~1e-4 (density at sea
level is unchanged since 0 m is still sampled exactly). Update the
calculate_density_profile doctest expected value accordingly.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Gui-FernandesBR

rocketpy/environment/environment.py

@@ -2617,7 +2617,7 @@ def calculate_density_profile(self):
         >>> env = Environment()
         >>> env.calculate_density_profile()
         >>> float(env.density(1000))
-        1.1115112430077818
+        1.1116196671683787
         """
         # Retrieve pressure P, gas constant R and temperature T
         P = self.pressure