[docs] [issue19504] Change "customise" to "customize".

Roundup Robot added the comment: New changeset 579360b1c8fe by Raymond Hettinger in branch '3.5': Issue 19504: Change "customise" to "customize" American spelling. https://hg.python.org/cpython/rev/579360b1c8fe ---------- _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue19504> _______________________________________