Fix install command

[adamchainz]

Using quotes within the square brackets fails with:

$ python -m pip install -U 'channels["daphne"]'
ERROR: Exception:
   ...
pip._vendor.packaging.requirements.InvalidRequirement: Parse error at "'["daphne'": Expected string_end

The quotes need only be around the whole reference, channels[daphne], for shell escaping.

[adamchainz]

Ah right, it is a Zsh thing, didn't realize that works on Bash.

[carltongibson]

On Bash you don't need the quotes at all, so it's only Apple switching here that has this come up... anyhooo... 😜

Thanks for the fix.