fix method reference to iter_markers in warning
fix method reference to iter_markers in warning

The-Compiler/pytest,hackebrot/pytest,markshao/pytest,pfctdayelise/pytest,davidszotten/pytest,pytest-dev/pytest,alfredodeza/pytest,tomviner/pytest,tomviner/pytest,nicoddemus/pytest,RonnyPfannschmidt/pytest,The-Compiler/pytest,ddboline/pytest,Akasurde/pytest,nicoddemus/pytest,txomon/pytest