[libxml2] Allow Python deprecation warnings for now

[Nick Wellnhofer <nwellnhof src gnome org>]

commit ebc04fec239e8821641719d13ad1f10acacd411b
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Fri Aug 26 15:10:06 2022 +0200

    Allow Python deprecation warnings for now
    
    See #208.

 .gitlab-ci.yml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index db987a7b..9ed7029c 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -42,7 +42,8 @@ gcc:minimum:
 gcc:python3:
   extends: .test
   variables:
-    CFLAGS: "-O2"
+    # TODO: Re-enable the warning after #208 is fixed.
+    CFLAGS: "-O2 -Wno-error=deprecated-declarations"
     PYTHON: "/usr/bin/python3"
 
 gcc:static: