serve.c: remove unnecessary include

Remove include "strvec.h" from serve.c, which is orphaned since
f0a35c9ce5 (serve: drop "keys" strvec, 2021-09-15)

Signed-off-by: Garrit Franke <garrit@slashdev.space>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

serve.c

@@ -3,7 +3,6 @@
 #include "config.h"
 #include "pkt-line.h"
 #include "version.h"
-#include "strvec.h"
 #include "ls-refs.h"
 #include "protocol-caps.h"
 #include "serve.h"