shell: Drop cargo-edit

This was used for "cargo upgrade" however there have been major
improvements to cargo since I added this and dependabot on GitHub
handles this better anyway.

One major downside of cargo-edit was that it would take a very long time
for the initial upgrade to occur, which made me use "cargo update" more
anyway to avoid the long wait times.

modules/shell.nix

@@ -110,7 +110,6 @@ in
           cargo-license
           cargo-feature
           cargo-tarpaulin
-          cargo-edit
           bacon
           clippy
           ;