Remove *.rej pattern from .gitignore

With commit 3f1b0e1f

 ".gitignore update"
Linus's current git tree starts to ignore any "*.rej" files.
So "git status" no longer shows these files, but the ones who works with
quilt patchsets, this not makes life easier as expected.
Because sometimes a work flow (at least for me) requires
"quilt push -f" followed by "git status" to see unresolved merge
conflicts, work on these conflicts to correct them and finalize
the patch with "quilt refresh".

And if there are some "*.rej" files exists in tree, for whatever
reason, this means something goes really wrong there and i think
this situation not deserves to be ignored.

Signed-off-by: S.Çağlar Onur <caglar@pardus.org.tr>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>