MINOR: server: remove fastinter from mistyped kw list

This keyword is already present in server kw list from checks.c.
diff --git a/src/server.c b/src/server.c
index 9a55d96..3362571 100644
--- a/src/server.c
+++ b/src/server.c
@@ -55,7 +55,7 @@
  */
 static const char *extra_kw_list[] = {
 	"ipv4", "ipv6", "legacy", "octet-count",
-	"fastinter", "fail-check", "sudden-death", "mark-down",
+	"fail-check", "sudden-death", "mark-down",
 	NULL /* must be last */
 };