modprobe: delete perror_exit() that makes no sense

Given modprobe -a, it's important to not exit early for a failure to
load a module; additionally, the rest of the code presumes that this
can fail without exiting.
diff --git a/toys/pending/modprobe.c b/toys/pending/modprobe.c
index 5431cb3..12d2d78 100644
--- a/toys/pending/modprobe.c
+++ b/toys/pending/modprobe.c
@@ -381,7 +381,6 @@
   }
   res = syscall(__NR_init_module, buf, len, toybuf);
   if (CFG_TOYBOX_FREE && buf != toybuf) free(buf);
-  if (res) perror_exit("failed to load %s ", toys.optargs[0]);
   return res;
 }