Do not break git-gui messages into multiple lines.

Do not break git-gui messages into multiple lines.

Many git-gui messages were broken into a multiple lines to make
good paragraph width. Unfortunately in reality it breaks the paragraph
width completely, because the dialog window width does not coincide
with the paragraph width created by the current font.

Tcl/Tk's standard dialog boxes are breaking the long lines
automatically, so it is better to make long lines and let the
interpreter do the job.

Signed-off-by: Eygene Ryabinkin <rea-git@codelabs.ru>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>