Makefile: Remove POT-Creation-Date from circuitpython.pot
Makefile: Remove POT-Creation-Date from circuitpython.pot

This line is only a magnet for conflicts; the date that circuitpython.pot
was modified can be extracted from git metadata.  Additionally, when
we add "make translate" checking to pre-commit, this will avoid spurious
changes since the most straightforward implementation would otherwise
update this line every time pre-commit executed.

adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython