Fix set expire test due to the new lazyfree configs changes (valkey-io#980)

Test failed because these two PRs valkey-io#865 and valkey-io#913.

Signed-off-by: Binbin <[email protected]>
Signed-off-by: Ping Xie <[email protected]>

Author: enjoy-binbin

tests/unit/type/string.tcl

@@ -631,9 +631,9 @@ if {[string match {*jemalloc*} [s mem_allocator]]} {
         assert_replication_stream $repl {
            {select *}
            {set foo bar}
-           {del foo}
+           {unlink foo}
            {set foo bar}
-           {del foo}
+           {unlink foo}
            {incr foo}
         }