Minor documentation problem

[kai11]

https://pythonhosted.org/Flask-Cache/

>>> adder1 = Adder()
>>> adder2 = Adder()
>>> adder1.add(3)
3.23214234
>>> adder2.add(3)
3.60898509
>>> cache.delete_memoized(adder.add)
>>> adder1.add(3)cache.delete_memoized(adder.add)

cache.delete_memoized(adder.add) line should refer to adder1