Improve display of channel specs within device specs with pprint

[HGSilveri]

Following #954, we can use pprint to impove the display of the channel specs in Device.print_specs() from this:

Channels:
 - 'rydberg_global': Rydberg(addressing='Global', max_abs_detuning=125.66370614359172, max_amp=12.566370614359172, min_retarget_interval=None, fixed_retarget_t=None, max_targets=None, clock_period=4, min_duration=16, max_duration=100000000, min_avg_amp=0, mod_bandwidth=8, custom_phase_jump_time=None, eom_config=RydbergEOM(limiting_beam=<RydbergBeam.RED: 2>, max_limiting_amp=188.49555921538757, intermediate_detuning=2827.4333882308138, controlled_beams=(<RydbergBeam.BLUE: 1>,), mod_bandwidth=40, custom_buffer_time=240, multiple_beam_control=True, blue_shift_coeff=1.0, red_shift_coeff=1.0), propagation_dir=None)

to this

Channels:
 - 'rydberg_global': Rydberg(addressing='Global',
        max_abs_detuning=125.66370614359172,
        max_amp=12.566370614359172,
        min_retarget_interval=None,
        fixed_retarget_t=None,
        max_targets=None,
        clock_period=4,
        min_duration=16,
        max_duration=100000000,
        min_avg_amp=0,
        mod_bandwidth=8,
        custom_phase_jump_time=None,
        eom_config=RydbergEOM(limiting_beam=<RydbergBeam.RED: 2>,
                              max_limiting_amp=188.49555921538757,
                              intermediate_detuning=2827.4333882308138,
                              controlled_beams=(<RydbergBeam.BLUE: 1>,),
                              mod_bandwidth=40,
                              custom_buffer_time=240,
                              multiple_beam_control=True,
                              blue_shift_coeff=1.0,
                              red_shift_coeff=1.0),
        propagation_dir=None)

[HGSilveri]

Well, apparently this works with Python 3.9 too 😅