Auto merge of #12188 - epage:git, r=weihanglo

test(add): Remove expensive test

This is a carry-over from cargo-edit where we had to worry about the UX of all of the behavior while now we are just relying on built-in cargo behavior and don't need to test it specifically for `cargo add`.

On my machine, this test takes 11s.

Author: bors

tests/testsuite/cargo_add/invalid_git_external/in

@@ -36,7 +36,6 @@ mod git_rev;
 mod git_tag;
 mod infer_prerelease;
 mod invalid_arg;
-mod invalid_git_external;
 mod invalid_git_name;
 mod invalid_key_inherit_dependency;
 mod invalid_key_overwrite_inherit_dependency;