patch 8.2.0966: 'shortmess' flag "n" not used in two places

Problem:    'shortmess' flag "n" not used in two places.
Solution:   Make use of the "n" flag consistent. (Nick Jensen, closes #6245,
            closes #6244)
diff --git a/src/bufwrite.c b/src/bufwrite.c
index f189551..4be48e2 100644
--- a/src/bufwrite.c
+++ b/src/bufwrite.c
@@ -598,6 +598,12 @@
 }
 #endif // UNIX
 
+    char *
+new_file_message(void)
+{
+    return shortmess(SHM_NEW) ? _("[New]") : _("[New File]");
+}
+
 /*
  * buf_write() - write to file "fname" lines "start" through "end"
  *
@@ -2347,7 +2353,7 @@
 	}
 	else if (newfile)
 	{
-	    STRCAT(IObuff, shortmess(SHM_NEW) ? _("[New]") : _("[New File]"));
+	    STRCAT(IObuff, new_file_message());
 	    c = TRUE;
 	}
 	if (no_eol)