Increase timeline avatar size to 32x32px


Above image contains my avatar shown two times, the first time is with the `` element expanded to 32x32px, and the second (at the bottom) is the 30x30px default.

Currently, conduit, synapse, dendrite, and the media repo all send a 32x32px image when requested to send a 30x30px one, this results in that *slight* blur you see right there (on the bottom image)

Then, changing the default avatar (request and frame) size to 32x32px seems like a sensible change, imo.

Start by tracing the timeline avatar rendering and the request and frame sizes described in the issue. Check how the current 30x30px default is applied, then verify that the timeline uses 32x32px consistently and the displayed avatar no longer has the reported blur.

Written by the indexing model from the issue text.