fix(messages): improve deadly signal messages #32364

Problem:
Deadly signal messages mention "Vim", and add redundant newlines.

Solution:
- Update the messages.
- Don't add an extra newline.

src/nvim/os/signal.c

@@ -175,7 +175,7 @@ static void deadly_signal(int signum)
 
   ILOG("got signal %d (%s)", signum, signal_name(signum));
 
-  snprintf(IObuff, IOSIZE, "Vim: Caught deadly signal '%s'\r\n", signal_name(signum));
+  snprintf(IObuff, IOSIZE, "Nvim: Caught deadly signal '%s'\n", signal_name(signum));
 
   // Preserve files and exit.
   preserve_exit(IObuff);