CLN: Remove tmp.xlsx
For some reason a file, `tmp.xlsx`, got included in this commit. https://github.com/pandas-dev/pandas/pull/24086/files#diff-0a840748858a9d8ed007d67b7c7c5fef

Contents are the same as this docstring: https://github.com/pandas-dev/pandas/blob/master/pandas/io/excel.py#L251

