nitpick: html <-> pdf

[haraldschilly]

it says html, but copies pdf and vice versa

documentation/prepare.py

Line 55 in 9e31ca4

sp.call(f"rsync -rlp --delete {sage_root}/local/share/doc/sage/pdf ./".split(), stdout=sp.PIPE)

[haraldschilly]

Apart from that this was the first time the new prepare.py was used to build the documentation and it worked fine.