Fix a few more instances of matrix-doc being used; Fix changelog support for repo split (#1051)

* Use spec-proposals repo for links in spec text and current changelog

* Make the changelog repo-aware

* Changelog

content/client-server-api/_index.md

@@ -1490,7 +1490,7 @@ before using the contents verbatim.
 **It is not safe to assume that an event body will have all the expected
 fields of the expected types.**
 
-See [MSC2801](https://github.com/matrix-org/matrix-doc/pull/2801) for more
+See [MSC2801](https://github.com/matrix-org/matrix-spec-proposals/pull/2801) for more
 detail on why this assumption is unsafe.
 {{% /boxes/warning %}}
 

content/client-server-api/modules/instant_messaging.md

@@ -102,7 +102,7 @@ the tag entirely.
 {{% boxes/note %}}
 A future iteration of the specification will support more powerful and
 extensible message formatting options, such as the proposal
-[MSC1767](https://github.com/matrix-org/matrix-doc/pull/1767).
+[MSC1767](https://github.com/matrix-org/matrix-spec-proposals/pull/1767).
 {{% /boxes/note %}}
 
 {{% msgtypes %}}

content/client-server-api/modules/moderation_policies.md

@@ -53,7 +53,7 @@ follows:
 -   Is a `room` rule...
     -   Applied to a user: The user should leave the room and not join
         it
-        ([MSC2270](https://github.com/matrix-org/matrix-doc/pull/2270)-style
+        ([MSC2270](https://github.com/matrix-org/matrix-spec-proposals/pull/2270)-style
         ignore).
     -   Applied to a room: No-op because a room cannot ban itself.
     -   Applied to a server: The server should prevent users from
@@ -120,6 +120,6 @@ Depending on how implementations handle subscriptions, user IDs may be
 linked to policy lists and therefore expose the views of that user. For
 example, a client implementation which joins the user to the policy room
 would expose the user's ID to observers of the policy room. In future,
-[MSC1228](https://github.com/matrix-org/matrix-doc/pulls/1228) and
-[MSC1777](https://github.com/matrix-org/matrix-doc/pulls/1777) (or
+[MSC1228](https://github.com/matrix-org/matrix-spec-proposals/pulls/1228) and
+[MSC1777](https://github.com/matrix-org/matrix-spec-proposals/pulls/1777) (or
 similar) could help solve this concern.