fix: shellcheck errors

[dijonkitchen]

Resolves #3081

[ljharb]

is the intention here that if cdnvm fails, the alias should not be set?

[dijonkitchen]

Yes, this was meant to address https://www.shellcheck.net/wiki/SC2164, but I think it's surprising with the reordering which was meant to keep the cdnvm code together and the alias after and separate since shellcheck advised against using an alias in the same parsing unit: https://www.shellcheck.net/wiki/SC2262

To adhere more to the principle of least surprise, I'm going to reorder it back and still have the exit:

# ...
alias cd='cdnvm'
cdnvm "$PWD" || exit
# ...