MINOR: tcp: avoid confusion in time parsing init

We never enter val_fc_time_value when an associated fetcher such as `fc_rtt` is
called without argument.  meaning `type == ARGT_STOP` will never be true and so
the default `data.sint = TIME_UNIT_MS` will never be set.  remove this part to
avoid thinking default data.sint is set to ms while reading the code.

Signed-off-by: William Dauchy <w.dauchy@criteo.com>

[Cf: This patch may safely backported as far as 1.7. But no matter if not.]
diff --git a/src/proto_tcp.c b/src/proto_tcp.c
index 3dfc6a6..b136a60 100644
--- a/src/proto_tcp.c
+++ b/src/proto_tcp.c
@@ -1580,10 +1580,6 @@
  */
 static int val_fc_time_value(struct arg *args, char **err)
 {
-	if (args[0].type == ARGT_STOP) {
-		args[0].type = ARGT_SINT;
-		args[0].data.sint = TIME_UNIT_MS;
-	}
 	if (args[0].type == ARGT_STR) {
 		if (strcmp(args[0].data.str.area, "us") == 0) {
 			free(args[0].data.str.area);