Don't enforce MXC URIs, but also don't confuse people

event-schemas/schema/core-event-schema/msgtype_infos/image_info.yaml

@@ -19,8 +19,8 @@ properties:
     type: integer
   thumbnail_url:
     description: |-
-      The `MXC URI`_ to a thumbnail of the image. Only present if the
+      The URL (typically `MXC URI`_) to a thumbnail of the image.
-      thumbnail is unencrypted.
+      Only present if the thumbnail is unencrypted.
     type: string
   thumbnail_file:
     description: |-

event-schemas/schema/m.room.message$m.audio

@@ -27,7 +27,9 @@ properties:
           - m.audio
         type: string
       url:
-        description: Required if the file is not encrypted. The `MXC URI`_ to the audio clip.
+        description: |-
+          Required if the file is not encrypted. The URL (typically `MXC URI`_)
+          to the audio clip.
         type: string
       file:
         description: |-

event-schemas/schema/m.room.message$m.file

@@ -42,7 +42,9 @@ properties:
           - m.file
         type: string
       url:
-        description: Required if the file is unencrypted. The `MXC URI`_ to the file.
+        description: |-
+          Required if the file is unencrypted. The URL (typically `MXC URI`_)
+          to the file.
         type: string
       file:
         description: |-

event-schemas/schema/m.room.message$m.image

@@ -17,7 +17,9 @@ properties:
           - m.image
         type: string
       url:
-        description: Required if the file is unencrypted. The `MXC URI`_ to the image.
+        description: |-
+          Required if the file is unencrypted. The URL (typically `MXC URI`_)
+          to the image.
         type: string
       file:
         description: |-

event-schemas/schema/m.room.message$m.video

@@ -28,8 +28,8 @@ properties:
             type: integer
           thumbnail_url:
             description: |-
-              The `MXC URI`_ to an image thumbnail of the video clip. Only present if the
+              The URL (typically `MXC URI`_) to an image thumbnail of
-              thumbnail is unencrypted.
+              the video clip. Only present if the thumbnail is unencrypted.
             type: string
           thumbnail_file:
             description: |-
@@ -48,7 +48,9 @@ properties:
           - m.video
         type: string
       url:
-        description: Required if the file is unencrypted. The `MXC URI`_ to the video clip.
+        description: |-
+          Required if the file is unencrypted. The URL (typically `MXC URI`_)
+          to the video clip.
         type: string
       file:
         description: |-