Fix typo

[taji-taji]

I found what seems to be a typo in the description of the install subcommand and have corrected it.

[xtremekforever]

LOL, a double they they!

[cmcgee1024]

Thank you for your contribution. Fixing the wording there will not only help with what people see when they invoke swiftly install --help, but it will also fix the DocC documentation too. https://swiftpackageindex.com/swiftlang/swiftly/0.4.0-dev/documentation/swiftlydocs/swiftly-cli-reference#install

At the moment, there is unfortunately a manual step to regenerate the documentation from the comment change. Can you run the following, commit the update the markdown and add it here?

swift package plugin generate-docs-reference

[taji-taji]

@cmcgee1024
Thank you for your review!
I also updated the markdown of the document.

[cmcgee1024]

Thanks again @taji-taji