Link to "First Steps" has wrong URL

[pkofod]

The link to the “First Steps” subcategory in the description of “Usage” is wrong, as it has “usage” in the URL instead of “user”, that is https://discourse.julialang.org/c/usage/first-steps vs https://discourse.julialang.org/c/user/first-steps

[vchuravy]

Thank you. Fixed.