Update links to RFC9110 (#520)

We rolled back on the change introduced in #452 and now use the more
readable `httpwg.org` version of RFC9110 to populate the cross-references
database. We also updated Specref to return the `httpwg.org` URL for that
spec.

This means that the cross-references database no longer has the section IDs
and rather has the field name. This update rolls back the changes in #452
accordingly.

spec/index.bs

@@ -1505,7 +1505,7 @@ The [=well-known file=] is fetched in the [=fetch the config file=] algorithm:
 (a) **without** cookies,
 (b) **with** the <a http-header>Sec-Fetch-Dest</a> header set to `webidentity`, and
 (c) **without** revealing the [=RP=] in the <a http-header>Origin</a> or
-    [[RFC9110#section-10.1.3|Referer]] headers.
+    [[RFC9110#field.referer|Referer]] headers.
 
 For example:
 
@@ -1539,8 +1539,8 @@ The [=config file=] is fetched in the [=fetch the config file=] algorithm:
 (a) **without** cookies,
 (b) **with** the <a http-header>Sec-Fetch-Dest</a> header set to `webidentity`,
 (c) **without** revealing the [=RP=] in the <a http-header>Origin</a> or
-    [[RFC9110#section-10.1.3|Referer]] headers, and
-(d) **without** following [[RFC9110#section-10.2.2|HTTP redirects]].
+    [[RFC9110#field.referer|Referer]] headers, and
+(d) **without** following [[RFC9110#field.location|HTTP redirects]].
 
 For example:
 
@@ -1645,8 +1645,8 @@ The [=accounts list endpoint=] is fetched in the [=fetch the accounts list=] alg
 (a) **with** [=IDP=] cookies,
 (b) **with** the <a http-header>Sec-Fetch-Dest</a> header set to `webidentity`,
 (c) **without** revealing the [=RP=] in the <a http-header>Origin</a> or
-    [[RFC9110#section-10.1.3|Referer]] headers, and
-(d) **without** following [[RFC9110#section-10.2.2|HTTP redirects]].
+    [[RFC9110#field.referer|Referer]] headers, and
+(d) **without** following [[RFC9110#field.location|HTTP redirects]].
 
 For example:
 
@@ -1724,7 +1724,7 @@ The [=client metadata endpoint=] is fetched in the [=fetch the client metadata=]
 (a) **without** cookies,
 (b) **with** the <a http-header>Sec-Fetch-Dest</a> header set to `webidentity`,
 (c) **with** the [=RP=]'s origin in the <a http-header>Origin</a> header, and
-(d) **without** following [[RFC9110#section-10.2.2|HTTP redirects]].
+(d) **without** following [[RFC9110#field.location|HTTP redirects]].
 
 The user agent also passes the **client_id**.
 
@@ -1774,7 +1774,7 @@ The [=identity assertion endpoint=] is fetched in the [=fetch an identity assert
 (b) **with** [=IDP=] cookies,
 (c) **with** the [=RP=]'s origin in the <a http-header>Origin</a> header, and
 (d) **with** the <a http-header>Sec-Fetch-Dest</a> header set to `webidentity`,
-(e) **without** following [[RFC9110#section-10.2.2|HTTP redirects]].
+(e) **without** following [[RFC9110#field.location|HTTP redirects]].
 
 It will also contain the following parameters in the request body `application/x-www-form-urlencoded`: