refactor: allow dead_code StringError::new

Author: Joonas Koivunen

http/src/v0/support.rs

@@ -117,6 +117,8 @@ impl<D: std::fmt::Display> From<D> for StringError {
 }
 
 impl StringError {
+    // Allowing this as dead since it hopefully doesn't stay unused for long
+    #[allow(dead_code)]
     pub fn new(cow: Cow<'static, str>) -> Self {
         StringError(cow)
     }