fix lints

Cargo.toml

@@ -525,9 +525,6 @@ single_use_lifetimes = "warn"
 unsafe_op_in_unsafe_fn = "warn"
 unreachable_pub = "warn"
 
-# not in rust 1.75.0 (doesn't break CI but won't check for it)
-unit_bindings = "warn"
-
 # this seems to suggest broken code and is not working correctly
 unused_braces = "allow"
 
@@ -577,7 +574,6 @@ filetype_is_file = "warn"
 float_cmp_const = "warn"
 format_push_string = "warn"
 impl_trait_in_params = "warn"
-ref_to_mut = "warn"
 lossy_float_literal = "warn"
 mem_forget = "warn"
 missing_assert_message = "warn"