CLEANUP: contrib/prometheus-exporter: remove unused includes

unless I'm wrong, those includes are no longer needed.  The only recent
one I remember is ssl-sock include since commit
5d9b8f3c93 ("MINOR:
contrib/prometheus-exporter: use fill_info for process dump") where we
make use of the code from stats.c

Signed-off-by: William Dauchy <wdauchy@gmail.com>

contrib/prometheus-exporter/service-prometheus.c

@@ -19,8 +19,6 @@
 #include <haproxy/backend.h>
 #include <haproxy/cfgparse.h>
 #include <haproxy/check.h>
-#include <haproxy/compression.h>
-#include <haproxy/dns.h>
 #include <haproxy/frontend.h>
 #include <haproxy/global.h>
 #include <haproxy/http.h>
@@ -29,12 +27,9 @@
 #include <haproxy/list.h>
 #include <haproxy/listener.h>
 #include <haproxy/log.h>
-#include <haproxy/pipe.h>
-#include <haproxy/pool.h>
 #include <haproxy/proxy.h>
 #include <haproxy/sample.h>
 #include <haproxy/server.h>
-#include <haproxy/ssl_sock.h>
 #include <haproxy/stats.h>
 #include <haproxy/stream.h>
 #include <haproxy/stream_interface.h>