asciidoc: depends on python@2 for Linuxbrew
asciidoc: depends on python@2 for Linuxbrew

asciidoc is written in Python 2. I'm guessing this hasn't been updated
since `python` was changed to point to Python 3.

Closes Linuxbrew/homebrew-core#7847.

Signed-off-by: Michka Popoff <7b0496f66f66ee22a38826c310c38b415671b832@gmail.com>

maxim-belkin/homebrew-core,maxim-belkin/homebrew-core,rwhogg/homebrew-core,Linuxbrew/homebrew-core,Linuxbrew/homebrew-core,rwhogg/homebrew-core,LinuxbrewTestBot/homebrew-core,LinuxbrewTestBot/homebrew-core