[docs] PDF-Files only available in Letter-Format

*Dear Mr. van Rossum, * *dear members of the great Python-Team! * I want to thank you for your job and what you make available for the public! Please let my say, that there seams to be a little mistake in the PDF-Files you offered for download this night: In the ZIP-File " https://docs.python.org/3.7/archives/python-3.7.2-docs-pdf-a4.zip" there are PDF-Files in the Letter-Format as well - instead of A4-Format! With kind regards from Tübingen in Southern Germany, *Heinrich Ottinger*