CleanMX and MISP parser call deprecated utcfromtimestamp

[sebix]

Background: #2571

On Ubuntu 24.04 two bots fail our tests because datetime.datetime.fromtimestamp is deprecated:

DeprecationWarning: datetime.datetime.utcfromtimestamp() is deprecated and scheduled for removal in a future version.
Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.fromtimestamp(timestamp, datetime.UTC).

intelmq/bots/parsers/cleanmx/parser.py:                        value = (datetime.utcfromtimestamp(int(value)).isoformat() + " UTC")
intelmq/bots/parsers/misp/parser.py:                          datetime.utcfromtimestamp(float(timestamp))))