Remove unused remove_dir_all crate from sqlx-cli, fixes RUSTSEC-2023-0018

[aldur]

Fix #2755.

NOTES:

• The comment links to this issue, which relates to Windows. I don't have a Windows host handy to test, but I have seen that the CI covers it.
• Still, I have manually grepped for the three functions implemented by the crate at that version (https://docs.rs/remove_dir_all/0.7.0/remove_dir_all/index.html) and didn't find any reference in sqlx-cli.

[aldur]

Formatting fails on a file I haven't touched. Do you want me to fix it?

[abonander]

Looking through, we're also indirectly depending on remove_dir_all 0.5.3 via tempdir which hasn't been maintained in 5 years and is only used in one test. I'll fix that myself.