MDEV-19344 innodb.innodb-change-buffer-recovery fails

The test was incompatible with ./mtr --repeat=2 until
commit 2d6719d
fixed that.

It turns out that the failing assertion that we disabled in
commit 3db94d2
is bogus and can fail when the change buffer is emptied
during the last batch of crash recovery. The reason for this
is the condition around the page_create_empty() call in
page_cur_delete_rec(). The condition was removed in MariaDB
Server 10.5 as part of MDEV-12353, in
commit 7ae21b1 and
commit f8a9f90.

The bug that the assertion aimed to catch is MDEV-22497, which
was fixed in commit 26aab96.

storage/innobase/include/page0page.ic

@@ -173,9 +173,6 @@ page_header_set_field(
 {
 	ut_ad(page);
 	ut_ad(field <= PAGE_N_RECS);
-#if 0 /* FIXME: MDEV-19344 hits this */
-	ut_ad(field != PAGE_N_RECS || val);
-#endif
 	ut_ad(field == PAGE_N_HEAP || val < srv_page_size);
 	ut_ad(field != PAGE_N_HEAP || (val & 0x7fff) < srv_page_size);