[pan] fix (configure.ac): update GETTEXT version

[Dominique Dumont <ddumont src gnome org>]

commit 6afcdb824674e89ac070ee066d7656b19e779e72
Author: Dominique Dumont <dod debian org>
Date:   Wed Sep 1 18:03:37 2021 +0200

    fix (configure.ac): update GETTEXT version
    
    to avoid this error:
    
    *** error: gettext infrastructure mismatch: using a Makefile.in.in from gettext version 0.19 but the 
autoconf macros are from gettext version 0.20
    
    My Debian unstable has version 0.21, so let's try this on ubuntu...

 configure.ac | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/configure.ac b/configure.ac
index 69a1d4d2..e1f8ae01 100644
--- a/configure.ac
+++ b/configure.ac
@@ -94,7 +94,7 @@ AC_CHECK_HEADERS([errno.h fcntl.h])
 dnl I18n support
 GETTEXT_PACKAGE=pan
 AC_SUBST(GETTEXT_PACKAGE)
-AM_GNU_GETTEXT_VERSION([0.19.7])
+AM_GNU_GETTEXT_VERSION([0.21])
 AM_GNU_GETTEXT([external])
 AC_DEFINE_UNQUOTED([GETTEXT_PACKAGE], ["$GETTEXT_PACKAGE"], [Gettext Package])
 panlocaledir=[${datadir}/locale]