[metacity] build: remove AC_PREREQ

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 5d72f0da109603e1f66686547c6b96de1dcbf41e
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Sun Sep 20 01:16:02 2015 +0300

    build: remove AC_PREREQ

 configure.ac |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 350e5bf..61d58ad 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,5 +1,3 @@
-AC_PREREQ(2.50)
-
 m4_define([metacity_major_version], [3])
 m4_define([metacity_minor_version], [17])
 m4_define([metacity_micro_version], [2])