Remove old UI test (#1289)

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>

substrate/frame/support/test/tests/construct_runtime_ui.rs

@@ -27,6 +27,9 @@ fn ui() {
 	// As trybuild is using `cargo check`, we don't need the real WASM binaries.
 	std::env::set_var("SKIP_WASM_BUILD", "1");
 
+	// Deny all warnings since we emit warnings as part of a Runtime's UI.
+	std::env::set_var("RUSTFLAGS", "--deny warnings");
+
 	let t = trybuild::TestCases::new();
 	t.compile_fail("tests/construct_runtime_ui/*.rs");
 }