autoconf: Update .gitignore for move of version.m4.

https://github.com/libsdl-org/autoconf/commit/6027e993585cedbb4d7afbd9846b3a2c99ec093d

From 6027e993585cedbb4d7afbd9846b3a2c99ec093d Mon Sep 17 00:00:00 2001
From: Zack Weinberg <[EMAIL REDACTED]>
Date: Sun, 3 Oct 2021 18:15:20 -0400
Subject: [PATCH] Update .gitignore for move of version.m4.

Commit af5c11ed moved version.m4 from lib/m4sugar to lib, but did not
update .gitignore to match.
---
 .gitignore | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.gitignore b/.gitignore
index 21d51819..2144fca0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -69,7 +69,7 @@ Makefile.in
 /lib/autoscan/autoscan.list
 /lib/emacs/*.elc
 /lib/emacs/elc-stamp
-/lib/m4sugar/version.m4
+/lib/version.m4
 /log
 /man/*.[1-9]
 /man/autoscan.log