system/ui: fix cruise disabled state displaying "?" instead of "–"

[deanlee]

before:

after:

[sshane]

this breaks the spinner on devices without anything compiled

comma@comma-7e8e41ad:/data/openpilot$ git clean -xfd && rm -rf /data/scons_cache/ && ./launch_openpilot.sh
RAYLIB STATIC 5.5.0.2 LOADED
kj/filesystem-disk-unix.c++:1734: warning: PWD environment variable doesn't match current directory; pwd = /data/openpilot/system/manager
gbm_create_device(156): Info: backend name is: msm_drm
Traceback (most recent call last):
  File "/data/openpilot/system/ui/./spinner.py", line 106, in <module>
    main()
  File "/data/openpilot/system/ui/./spinner.py", line 95, in main
    gui_app.init_window("Spinner")
  File "/data/openpilot/openpilot/system/ui/lib/application.py", line 89, in init_window
    self._load_fonts()
  File "/data/openpilot/openpilot/system/ui/lib/application.py", line 221, in _load_fonts
    from openpilot.selfdrive.ui.onroad.hud_renderer import CRUISE_DISABLED_CHAR
  File "/data/openpilot/openpilot/selfdrive/ui/onroad/hud_renderer.py", line 4, in <module>
    from openpilot.selfdrive.ui.ui_state import ui_state, UIStatus
  File "/data/openpilot/openpilot/selfdrive/ui/ui_state.py", line 4, in <module>
    from openpilot.common.params import Params, UnknownKeyName
  File "/data/openpilot/openpilot/common/params.py", line 1, in <module>
    from openpilot.common.params_pyx import Params, ParamKeyType, UnknownKeyName
ModuleNotFoundError: No module named 'openpilot.common.params_pyx'

[sshane]

@deanlee should we add a constants file with no imports for stuff like this? Like C++ headers

reverted the import: a1ee5f5