doc: clarify special schemes

In url.md, describe "special" protocol schemes as "special" rather than
"considered to be special".

PR-URL: #28091
Reviewed-By: Michaël Zasso <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Trivikram Kamat <[email protected]>
Reviewed-By: Tiancheng "Timothy" Gu <[email protected]>

Author: Trott

doc/api/url.md

@@ -440,8 +440,8 @@ console.log(u.href);
 // fish://example.org
 ```
 
-The protocol schemes considered to be special by the WHATWG URL Standard
-include: `ftp`, `file`, `gopher`, `http`, `https`, `ws`, and `wss`.
+According to the WHATWG URL Standard, special protocol schemes are `ftp`,
+`file`, `gopher`, `http`, `https`, `ws`, and `wss`.
 
 #### url.search