Colons are inconsistently removed from connection errors

The bug

Some connection errors contain semicolons where they shouldn't. For example, the error Connection refused may be displayed to a user, but in other cases, a user may receive the error connection timed out: (ending with a colon).

In previous versions, both messages contained a colon (followed by the server address). However, the fix of MC-237608 changed the way in which these messages are displayed.

Expected behavior

The colons would be removed in all messages when not followed by any other information.