HVAC_MODE_ to be replaced by HVACMode.

[marni-xyz]

HVAC_MODE_ is a depracted constant. Will be removed in HA Core 2025.1

Just replace it in climate.py, lines 15 to 19.

Worked for me and the message disappeared.

Detailed error log:
HVAC_MODE_AUTO was used from blauberg_s21, this is a deprecated constant which will be removed in HA Core 2025.1. Use HVACMode.AUTO instead, please report it to the author of the 'blauberg_s21' custom integration
HVAC_MODE_COOL was used from blauberg_s21, this is a deprecated constant which will be removed in HA Core 2025.1. Use HVACMode.COOL instead, please report it to the author of the 'blauberg_s21' custom integration
HVAC_MODE_FAN_ONLY was used from blauberg_s21, this is a deprecated constant which will be removed in HA Core 2025.1. Use HVACMode.FAN_ONLY instead, please report it to the author of the 'blauberg_s21' custom integration
HVAC_MODE_HEAT was used from blauberg_s21, this is a deprecated constant which will be removed in HA Core 2025.1. Use HVACMode.HEAT instead, please report it to the author of the 'blauberg_s21' custom integration
HVAC_MODE_OFF was used from blauberg_s21, this is a deprecated constant which will be removed in HA Core 2025.1. Use HVACMode.OFF instead, please report it to the author of the 'blauberg_s21' custom integration