DOC: Correct test path in boilerplate.py docstring

Author: lucaznch

tools/boilerplate.py

@@ -11,7 +11,7 @@
 of Figure and Axes. Whenever the API of one of the wrapped methods changes,
 this script has to be rerun to keep pyplot.py up to date.
 
-The test ``lib/matplotlib/test_pyplot.py::test_pyplot_up_to_date`` checks
+The test ``lib/matplotlib/tests/test_pyplot.py::test_pyplot_up_to_date`` checks
 that the autogenerated part of pyplot.py is up to date. It will fail in the
 case of an API mismatch and remind the developer to rerun this script.
 """