Subs_filter module: use verstion with PCRE2 support.

contrib/src/ngx_http_substitutions_filter_module/version

diff --git a/contrib/src/ngx_http_substitutions_filter_module/version b/contrib/src/ngx_http_substitutions_filter_module/version
index e809e30..907abb5 100644
--- a/contrib/src/ngx_http_substitutions_filter_module/version
+++ b/contrib/src/ngx_http_substitutions_filter_module/version
@@ -1,2 +1,2 @@
 SUBSTITUTIONS_FILTER_NGINX_MODULE_VERSION := 0.6.4
-SUBSTITUTIONS_FILTER_NGINX_MODULE_GITHASH := b8a71eacc7f986ba091282ab8b1bbbc6ae1807e0
+SUBSTITUTIONS_FILTER_NGINX_MODULE_GITHASH := c6f825fa592acc29275c2eb4d1ab1eccab9de19e