Revert "flatpak: Fix gmime build"

The patch got merged upstream, so no need for us to carry it anymore.

This reverts commit 2572bef6dd.

build-aux/patches/gmime-autogen.sh-Also-allow-automake-1.18.patch

@@ -1,25 +0,0 @@
-From 22bb4d88a62924ceaf358e5c9871dbe05ae3464c Mon Sep 17 00:00:00 2001
-From: Niels De Graef <ndegraef@redhat.com>
-Date: Mon, 24 Nov 2025 00:38:22 +0100
-Subject: [PATCH] autogen.sh: Also allow automake 1.18
-
----
- autogen.sh | 2 +-
- 1 file changed, 1 insertion(+), 1 deletion(-)
-
-diff --git a/autogen.sh b/autogen.sh
-index af13973f..8dc5437e 100755
---- a/autogen.sh
-+++ b/autogen.sh
-@@ -57,7 +57,7 @@ fi
- 	DIE=1
- }
- 
--for automake_version in 1.9 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17; do
-+for automake_version in 1.9 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18; do
-     if automake-${automake_version} --version < /dev/null > /dev/null 2>&1 ; then
-         AUTOMAKE=automake-${automake_version}
-         ACLOCAL=aclocal-${automake_version}
--- 
-2.51.1
-