[test] Reduce number of iterations for slow test

Bug: v8:12591
Change-Id: Ica2ee1bb74d4b6f7e5ed06e23511c860bcf204be
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3456083Reviewed-by: Emanuel Ziegler <ecmziegler@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79050}

test/mjsunit/regress/regress-crbug-1276923.js

@@ -21,7 +21,7 @@ foo();
 
 // Stress execution with GCs.
 function bar() {
-  for (let cnt = 0, i = 655; cnt < 50000 && i !== 1; cnt++, i = i / 3) {
+  for (let cnt = 0, i = 655; cnt < 10000 && i !== 1; cnt++, i = i / 3) {
     i %= 2;
     const c = { "b": 1, "a":1, "c": 1,  "d": 1 };
     eval();