Revert http client changes (#18892)

These proved to be too unstable. Will restore these changes once the issues have been fixed.

Release Notes:

- N/A

crates/gpui/src/app.rs

@@ -1533,8 +1533,4 @@ impl HttpClient for NullHttpClient {
     fn proxy(&self) -> Option<&http_client::Uri> {
         None
     }
-
-    fn type_name(&self) -> &'static str {
-        type_name::<Self>()
-    }
 }