Mailing list mode: get rid of long prefixes

It’s the alt name tag, which is not helpful here.

<img src=3D"https:// community. openstreetmap. org /uploads/default/optim=
ized/1X/7099df9fca21e2e2d9e7561d9d17ef37cb8ce975_2_689x113.png" alt=3D"im=
agen" data-base62-sha1=3D"g479fzprovk1PRQcCp0fmJOVzSt" width=3D"auto" hei=
ght=3D"auto" srcset=3D"https:// community. openstreetmap. org/uploads/defaul=
t/optimized/1X/7099df9fca21e2e2d9e7561d9d17ef37cb8ce975_2_689x113.png, ht=
tps: // community. openstreetmap. org/uploads/default/optimized/1X/7099df9fca=
21e2e2d9e7561d9d17ef37cb8ce975_2_1033x169.png 1.5x, https:// community. ope=
nstreetmap. org/uploads/default/original/1X/7099df9fca21e2e2d9e7561d9d17ef=
37cb8ce975.png 2x" data-small-upload=3D"https:// community . openstreetmap.o=
rg/uploads/default/optimized/1X/7099df9fca21e2e2d9e7561d9d17ef37cb8ce975_=
2_10x10.png" style=3D"max-width: 100%;">

The forum does create overly complicated, but poor HTML code.
But the links here were broken manually since I’m allowed to write max. two links only.