chore: Dont check must_use

See rust-lang/rust-clippy#8339

Author: epage

Cargo.toml

@@ -81,7 +81,6 @@ rc_mutex = "warn"
 redundant_feature_names = "warn"
 ref_option_ref = "warn"
 rest_pat_in_fully_bound_structs = "warn"
-return_self_not_must_use = "warn"
 same_functions_in_if_condition = "warn"
 self_named_module_files = "warn"
 semicolon_if_nothing_returned = "warn"