test(help): Ensure consistent behavior regardless of rustup use

Author: epage

tests/testsuite/cargo/help/mod.rs

@@ -6,6 +6,8 @@ use cargo_test_support::str;
 fn case() {
     snapbox::cmd::Command::cargo_ui()
         .arg("--help")
+        .env_remove("RUSTUP_HOME") // consistent behavior with/without
+        .env_remove("RUSTUP_TOOLCHAIN")
         .assert()
         .success()
         .stdout_eq(file!["stdout.term.svg"])