[pygobject] meson: track pycairo-1.18 branch in the pycairo subproject

[Christoph Reiter <creiter src gnome org>]

commit 091b5eb27131d446119fef3a84488636de25f9c7
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Fri Jan 24 09:36:26 2020 +0100

    meson: track pycairo-1.18 branch in the pycairo subproject
    
    It still supports Python 2

 subprojects/pycairo.wrap | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/subprojects/pycairo.wrap b/subprojects/pycairo.wrap
index 87eac571..ba1c6568 100644
--- a/subprojects/pycairo.wrap
+++ b/subprojects/pycairo.wrap
@@ -1,4 +1,4 @@
 [wrap-git]
 directory=pycairo
 url=https://github.com/pygobject/pycairo.git
-revision=master
+revision=pycairo-1.18