Improve text for error "No issue found for given params" in UI

When attempting to add a non-issue URL or ID as a linked issue, the following message appears. It should be improved to something like "No matching issue found" or "No issue found at specified ID or URL".

Refraining from raising an MR as I'm not sure if it's just one of these instances that should be changed.

Assigning to @msedlakjakubowski for a first look.