make bubble layout try to use as much width as the mediatile allow

Author: Siriusmart

packages/shared-components/__vis__/linux/__baselines__/room/timeline/event-tile/call/ongoing/dm/DmOngoingCallTileView.stories.tsx/voice-call-in-progress-auto.png

@@ -1,5 +1,12 @@
 .container {
-    max-width: var(--MediaPreview-width);
+    /* A definite width, not just a cap. Bubble layout sizes the event line with
+       `width: fit-content`, so a container with only a `max-width` is sized
+       intrinsically -- and the icon beside the filename is a `height: 100%`
+       square, which contributes no width while an intrinsic width is being
+       computed. The tile would come out one icon too narrow and the filename
+       would be squeezed into an ellipsis. */
+    width: var(--MediaPreview-width);
+    max-width: 100%;
 
     display: flex;
     flex-direction: column;