[contracts] stabilize seal_code_hash, seal_set_code_hash and seal_own_code_hash (#11337)

* stabilize seal_code_hash, seal_set_code_hash, seal_own_code_hash

* fix missed place found by CI

* Fixed missed __unstable__

Co-authored-by: Alexander Theißen <alex.theissen@me.com>

substrate/frame/contracts/src/tests.rs

@@ -3088,7 +3088,6 @@ fn code_rejected_error_works() {
 }
 
 #[test]
-#[cfg(feature = "unstable-interface")]
 fn set_code_hash() {
 	let (wasm, code_hash) = compile_module::<Test>("set_code_hash").unwrap();
 	let (new_wasm, new_code_hash) = compile_module::<Test>("new_set_code_hash_contract").unwrap();