[nit] Remove or soften border-radius on message selection

[ShadowJonathan]

Is your suggestion related to a problem? Please describe.

To me this looks a tad out-of-place, but views differ.

For comparison;

After;

A bit of context

I think these were added to somewhat emulate discord Embeds, which currently look like this;

However, in my opinion, this only works as it is an inline "object", while the message selection looks slightly awkward to have rounded corners like that.

Alternatives

An alternative would be to change the corners to 2px or 4px, here's how that looks;

2px;

4px;