Dependency: update mod_pagespeed to the latest version (#1602)

diff --git a/testing-dependencies/mod_pagespeed b/testing-dependencies/mod_pagespeed
index 7cc8fa3..a863f1d 160000
--- a/testing-dependencies/mod_pagespeed
+++ b/testing-dependencies/mod_pagespeed
@@ -1 +1 @@
-Subproject commit 7cc8fa303e3c06ab058286c5a20ee321e4ef1e15
+Subproject commit a863f1d50641ea22a9a40859b7ae98b223858db1