gh-153926: Fix documented parameter name for `calendar.calendar` and `calendar.prcal...

gh-153926: Fix documented parameter name for `calendar.calendar` and `calendar.prcal` (#153927)

gh-153926: Fix documented parameter name for calendar.calendar and calendar.prcal

calendar.calendar() and calendar.prcal() are bound methods of the
module's TextCalendar instance, whose first parameter is named theyear,
but the documentation named it year, so the documented keyword raised
TypeError. Update the documentation to match the real signature, which
also matches the sibling month() and prmonth() functions.