Fixed the documentation for doctest_encoding.
Fixed the documentation for doctest_encoding.

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