Wiki update for v6 (virtual_env -> python)

[jasonhu5]

Describe the bug

The Wiki page "Configuration" is outdated (as marked on top of the page). This is probably a quick fix so I'm submitting this.

By following it to add virtual_env as a prompt item, the following error appears upon opening a new terminal:

fish: Unknown command: _tide_item_virtual_env
~/.config/fish/functions/_tide_1_line_prompt.fish (line 4): 
        _tide_item_$item
        ^~~~~~~~~~~~~~~^
in function '_tide_1_line_prompt'
in command substitution

Steps to reproduce

1. set --universal tide_left_prompt_items status context pwd git virtual_env
2. open a new fish shell window
3. See error pasted above

Environment

Output of tide bug-report:

fish version: 3.6.1
tide version: 6.0.1
term: screen-256color
os: Ubuntu 22.04
terminal emulator: X-terminal-emulator
fish startup: 14.42 millis
fisher plugins: jorgebucaran/fisher patrickf1/fzf.fish ilancosman/tide edc/bass

Additional context

Because of this commit: 10a1fab, the virtual_env entries on the Configuration Wiki should be replaced with python.

(I'm not sure about the workflow to contribute to Wiki pages, so just creating an issue here)

(Also, feel free to close this if the Wiki update has been planned for a later time)