[master] 2de23ed87 varnish.m4: Bump varnish.m4 to reflect minor changes

[Dridi Boukelmoune]

commit 2de23ed87e0e5c3f671bf55ffa60a3c66d6c9185
Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
Date:   Wed Mar 6 12:39:06 2024 +0100

    varnish.m4: Bump varnish.m4 to reflect minor changes

diff --git a/varnish.m4 b/varnish.m4
index e7e596717..83d80f2c9 100644
--- a/varnish.m4
+++ b/varnish.m4
@@ -31,7 +31,7 @@
 # OF THE POSSIBILITY OF SUCH DAMAGE.
 
 # varnish.m4 - Macros to build against Varnish.         -*- Autoconf -*-
-# serial 11 (varnish-6.5.0)
+# serial 12 (varnish-7.5.0)
 #
 # This collection of macros helps create VMODs or tools interacting with
 # Varnish Cache using the GNU build system (autotools). In order to work