Fix go.mod for tools and update go to 1.21

[rdimitrov]

The following PR updates the go.mod dependencies for tools fixing the make bootstrap failure from #1317

Closes #1317

[eleftherias]

The files in internal/db/ are out of date (it's only the comment that includes the version that needs to change).
If you run make bootstrap and then make sqlc you'll see the changes locally.

[rdimitrov]

The files in internal/db/ are out of date (it's only the comment that includes the version that needs to change). If you run make bootstrap and then make sqlc you'll see the changes locally.

Yeah, I just did that, I realised I forgot to generate.