Remove hg as default SchemeArgs

Summary:
## This stack
See D70553117 for context

## This diff
Diff #4: Change the default value of the SchemeArgs from vec![hg] to an empty vector.

This is the last diff that actually makes the E2E change. It changes the default in the argument, to support not specifying a scheme.

I update

Reviewed By: markbt

Differential Revision: D70561712

fbshipit-source-id: b11dafa93c2e02fac394b26a08eded05e4d496d9

Author: gustavoavena

eden/mononoke/scs/client/src/args/commit_id.rs

@@ -68,18 +68,9 @@ impl Scheme {
 
 #[derive(Args, Clone)]
 pub(crate) struct SchemeArgs {
-    #[clap(
-        long,
-        short('S'),
-        default_value = "hg",
-        default_value_if("no_scheme", "true", None),
-        value_delimiter = ','
-    )]
+    #[clap(long, short('S'), required = false, value_delimiter = ',')]
     /// Commit identity schemes to display
     schemes: Vec<Scheme>,
-    /// Pass empty list of identity schemes (useful for testing)
-    #[clap(long, hide = true)]
-    no_scheme: bool,
 }
 
 impl SchemeArgs {