chore(tvix/eval): postpone use of "dep:" for a bit

The "dep:" syntax in Cargo.toml is very new; crate2nix master has
support for it, but they have not yet made a release with this
update, and therefore the crate2nix in nixpkgs does not yet support
it.

Could we avoid using "dep:" for a few weeks to give crate2nix a
chance to release so I can bump the version in nixpkgs?  I've opened
an issue asking crate2nix to make a release:

  https://github.com/kolloch/crate2nix/issues/264

I propose that if they haven't acted within a month we stop waiting
and revert this at that time.

Change-Id: I999a72429db667bedf4b2cdba27cb63b3f3d9657
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7350
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

tvix/eval/Cargo.toml

@@ -50,7 +50,7 @@ default = [ "repl", "impure", "arbitrary", "nix_tests" ]
 nix_tests = []
 
 # Enables building the binary (tvix-eval REPL)
-repl = [ "dep:rustyline", "dep:clap" ]
+repl = [ "rustyline", "clap" ]
 
 # Enables operations in the VM which depend on the ability to perform I/O
 impure = []