[PATCH] rebase: emit one "fatal" in "fatal: fatal: <error>"

The die() routine adds a "fatal: " prefix, there is no reason to add
another one. Fixes code added in e65123a71d0 (builtin rebase: support
`git rebase <upstream> <switch-to>`, 2018-09-04).

Signed-off-by: Ævar Arnfjörð Bjarmason <redacted>
---
 builtin/rebase.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/builtin/rebase.c b/builtin/rebase.c
index 33e09619005..66a0a0f0d03 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c

@@ -1918,7 +1918,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
                                                   &options.orig_head))
                        options.head_name = NULL;
                else
-                       die(_("fatal: no such branch/commit '%s'"),
+                       die(_("no such branch/commit '%s'"),
                            branch_name);
        } else if (argc == 0) {
                /* Do not need to switch branches, we are already on it. */