[TD-3722]<fix>: taosdemo performance regression due to always set random seed. (#5740)

Co-authored-by: NShuduo Sang <sdsang@taosdata.com>

src/kit/taosdemo/taosdemo.c

@@ -507,11 +507,6 @@ static void resetAfterAnsiEscape(void) {
 
 static int taosRandom()
 {
-  struct timeval tv;
-
-  gettimeofday(&tv, NULL);
-  srand(tv.tv_usec);
-
   return rand();
 }