./x check miri: enable check_only feature

Author: RalfJung

src/bootstrap/src/core/build_steps/check.rs

@@ -793,8 +793,7 @@ tool_check_step!(Clippy { path: "src/tools/clippy", mode: Mode::ToolRustcPrivate
 tool_check_step!(Miri {
     path: "src/tools/miri",
     mode: Mode::ToolRustcPrivate,
-    enable_features: ["stack-cache"],
-    default_features: false,
+    enable_features: ["check_only"],
 });
 tool_check_step!(CargoMiri { path: "src/tools/miri/cargo-miri", mode: Mode::ToolRustcPrivate });
 tool_check_step!(Rustfmt { path: "src/tools/rustfmt", mode: Mode::ToolRustcPrivate });