serde: Remove allow attribute that's no longer needed

crates/ruma-common/tests/serde/empty_strings.rs

@@ -1,6 +1,3 @@
-// https://github.com/rust-lang/rust-clippy/issues/8875
-#![allow(clippy::derive_partial_eq_without_eq)]
-
 mod string {
     use serde::{Deserialize, Serialize};
     use serde_json::{from_value as from_json_value, json, to_value as to_json_value};

crates/ruma-common/tests/serde/enum_derive.rs

@@ -1,6 +1,3 @@
-// https://github.com/rust-lang/rust-clippy/issues/8875
-#![allow(clippy::derive_partial_eq_without_eq)]
-
 use ruma_common::serde::StringEnum;
 use serde_json::{from_value as from_json_value, json, to_value as to_json_value};
 

crates/ruma-common/tests/serde/url_deserialize.rs

@@ -1,6 +1,3 @@
-// https://github.com/rust-lang/rust-clippy/issues/8875
-#![allow(clippy::derive_partial_eq_without_eq)]
-
 use assert_matches::assert_matches;
 use form_urlencoded::Serializer as Encoder;
 use ruma_common::serde::urlencoded;