BUILD: comp: include proxy.h from flt_http_comp.c

It's used for proxy_type_str() but the header was missing.
diff --git a/src/flt_http_comp.c b/src/flt_http_comp.c
index c212b9c..b6aeb2b 100644
--- a/src/flt_http_comp.c
+++ b/src/flt_http_comp.c
@@ -20,7 +20,7 @@
 #include <haproxy/http_htx.h>
 #include <haproxy/htx.h>
 #include <haproxy/list.h>
-#include <haproxy/proxy-t.h>
+#include <haproxy/proxy.h>
 #include <haproxy/sample.h>
 #include <haproxy/stream.h>
 #include <haproxy/tools.h>