[IMPR] fix typos and deprecate function in PageRelatedError
[IMPR] fix typos and deprecate function in PageRelatedError

Fix IDE warnings:
- deprecate getPage()
- fix param names in docstring

Change-Id: I9ceeea98e0903021be38499d98dea6d0844e58d8

wikimedia/pywikibot-core,wikimedia/pywikibot-core