update all IETF RFC links to new URL format

src/http/header/if_range.rs

@@ -8,7 +8,8 @@ use crate::error::ParseError;
 use crate::http::header;
 use crate::HttpMessage;
 
-/// `If-Range` header, defined in [RFC7233](http://tools.ietf.org/html/rfc7233#section-3.2)
+/// `If-Range` header, defined
+/// in [RFC 7233 §3.2](https://datatracker.ietf.org/doc/html/rfc7233#section-3.2)
 ///
 /// If a client has a partial copy of a representation and wishes to have
 /// an up-to-date copy of the entire representation, it could use the
@@ -24,18 +25,16 @@ use crate::HttpMessage;
 /// in Range; otherwise, send me the entire representation.
 ///
 /// # ABNF
-///
 /// ```text
 /// If-Range = entity-tag / HTTP-date
 /// ```
 ///
-/// # Example values
+/// # Example Values
 ///
 /// * `Sat, 29 Oct 1994 19:43:31 GMT`
 /// * `\"xyzzy\"`
 ///
 /// # Examples
-///
 /// ```
 /// use actix_web::HttpResponse;
 /// use actix_web::http::header::{EntityTag, IfRange};