Fix pytensor_cache clear

[ricardoV94]

I noticed cache clear wasn't working and always used purge instead. It was a mistake introduced by 671a821 (downstream of aesara-devs/aesara#1312).

This changed many time.time() to to time.perf_counter(). But here it was a mistake. The units are wrong for the logic used in refresh to denote files that are "too old", as it compares the age of a file with the os stats:

pytensor/pytensor/link/c/cmodule.py

Lines 369 to 375 in 8ebff26

	def last_access_time(path):
	"""
	Return the number of seconds since the epoch of the last access of a
	given file.
	"""
	return os.stat(path)[stat.ST_ATIME]

The whole thing is a bit over-engineered but I don't want to touch it.