patch 8.2.3986: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index b3ab214..351ce82 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -1862,7 +1862,7 @@
 {
     if (mch_nodetype(fname) == NODE_OTHER)
     {
-	semsg(_("E503: \"%s\" is not a file or writable device"), fname);
+	semsg(_(e_str_is_not_file_or_writable_device), fname);
 	return FAIL;
     }
     return OK;
@@ -2357,8 +2357,7 @@
 	if (buf->b_p_ro)
 	    emsg(_(e_readonly_option_is_set_add_bang_to_override));
 	else
-	    semsg(_("E505: \"%s\" is read-only (add ! to override)"),
-		    buf->b_fname);
+	    semsg(_(e_str_is_read_only_add_bang_to_override), buf->b_fname);
 	return TRUE;
     }