mktime/0: remove unnecessary length>=6 input requirement (#3162)

This check was redundant and useless since jv2tm() used to require 8
elements, and errored anyway if not enough elements were provided.
After commit bc96146, this check also prevents mktime/0 from accepting
now supported inputs with less than 8 elements.

Ref: #3070 (comment)

Reported-by: itchyny <itchyny@cybozu.co.jp>

src/builtin.c

@@ -1602,8 +1602,6 @@ static int jv2tm(jv a, struct tm *tm) {
 static jv f_mktime(jq_state *jq, jv a) {
   if (jv_get_kind(a) != JV_KIND_ARRAY)
     return ret_error(a, jv_string("mktime requires array inputs"));
-  if (jv_array_length(jv_copy(a)) < 6)
-    return ret_error(a, jv_string("mktime requires parsed datetime inputs"));
   struct tm tm;
   if (!jv2tm(a, &tm))
     return jv_invalid_with_msg(jv_string("mktime requires parsed datetime inputs"));

tests/jq.test

@@ -1610,6 +1610,10 @@ strftime("%Y-%m-%dT%H:%M:%SZ")
 [2024,2,15]
 "2024-03-15T00:00:00Z"
 
+mktime
+[2024,8,21]
+1726876800
+
 gmtime
 1425599507
 [2015,2,5,23,51,47,4,63]