Fixed double `be` word on monkeypatch docs page.
Fixed double `be` word on monkeypatch docs page.

alfredodeza/pytest,markshao/pytest,tomviner/pytest,tomviner/pytest,Akasurde/pytest,pytest-dev/pytest,nicoddemus/pytest,nicoddemus/pytest,The-Compiler/pytest,RonnyPfannschmidt/pytest,The-Compiler/pytest