t-reftable-block: remove unnecessary variable 'j'

Currently, there are two variables for array indices, 'i' and 'j'.
The variable 'j' is used only once and can be easily replaced with
'i'. Get rid of 'j' and replace its occurence with 'i'.

Mentored-by: Patrick Steinhardt <ps@pks.im>
Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Chandra Pratap <chandrapratap3519@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Chandra Pratap

t/unit-tests/t-reftable-block.c

@@ -29,7 +29,6 @@ static void t_block_read_write(void)
 	int ret;
 	struct block_reader br = { 0 };
 	struct block_iter it = BLOCK_ITER_INIT;
-	size_t j = 0;
 	struct strbuf want = STRBUF_INIT;
 
 	REFTABLE_CALLOC_ARRAY(block.data, block_size);
@@ -64,15 +63,14 @@ static void t_block_read_write(void)
 
 	block_iter_seek_start(&it, &br);
 
-	while (1) {
+	for (i = 0; ; i++) {
 		ret = block_iter_next(&it, &rec);
 		check_int(ret, >=, 0);
 		if (ret > 0) {
 			check_int(i, ==, N);
 			break;
 		}
-		check(reftable_record_equal(&recs[j], &rec, GIT_SHA1_RAWSZ));
-		j++;
+		check(reftable_record_equal(&recs[i], &rec, GIT_SHA1_RAWSZ));
 	}
 
 	for (i = 0; i < N; i++) {