Cleanup unnecessary break in remote.c

Cleanup unnecessary break in remote.c

This simple change makes the body of "case 0" easier to read; no
matter what the value of matched_src is we want to break out of
the switch and not fall through.  We only want to display an error
if matched_src is NULL, as this indicates there is no local branch
matching the input.

Also modified the default case's error message so it uses one less
line of text.  Even at 8 column per tab indentation we still don't
break 80 columns with this new formatting.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>