Fix failing IERS tests

[wtgee]

The CI testing is failing due to IERS inaccuracies.

Errors:

    def test_create_mount_simulator(config_host, config_port):
        # Use the simulator create function directly.
>       mount = create_mount_simulator()

tests/test_mount.py:27: 

and

E               astropy.utils.iers.iers.IERSRangeError: (some) times are outside of range covered by IERS table. Cannot convert with full accuracy. To allow conversion with degraded accuracy set astropy.utils.iers.conf.iers_degraded_accuracy to "warn" or "silent". For more information about setting this configuration parameter or controlling its value globally, see the Astropy configuration system documentation https://docs.astropy.org/en/stable/config/index.html.