Typo in variable PERCENT_40

[thomric2]

This variable is missing the letter P

python-pptx/src/pptx/enum/dml.py

Lines 253 to 254 in 278b47b

	ERCENT_40 = (6, "pct40", "40% of the foreground color.")
	"""40% of the foreground color."""

[scanny]

Hah! So it is. Thanks for pointing that out :)