Revert "Alias to keywords (eg source) (#4835)" (#4841)

This reverts commit c023d4111a.

crates/nu-command/tests/commands/alias.rs

@@ -1,13 +0,0 @@
-use nu_test_support::{nu, pipeline};
-
-#[test]
-fn echo_range_is_lazy() {
-    let actual = nu!(
-        cwd: "tests/fixtures/formats", pipeline(
-        r#"
-        alias bar = source sample_def.nu; bar; greet
-        "#
-    ));
-
-    assert_eq!(actual.out, "hello");
-}