Re-enable shared-memory tests under tsan/stress_incremental_marking

The underlying issue was fixed with https://crrev.com/c/3660258

Bug: v8:12883
Change-Id: If7a1fdaf122396396cfbaaae3a68ef89bafc1703
Cq-Include-Trybots: luci.v8.try:v8_linux64_tsan_rel_ng
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3663342
Auto-Submit: Patrick Thier <pthier@chromium.org>
Reviewed-by: Shu-yu Guo <syg@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80728}

test/mjsunit/mjsunit.status

@@ -1474,10 +1474,6 @@
 ##############################################################################
 ['variant == stress_incremental_marking', {
   'wasm/shared-memory-worker-stress': [PASS, SLOW, ['tsan', SKIP]],
-
-  # https://crbug.com/v8/12883
-  'shared-memory/shared-string': [PASS, ['tsan', SKIP]],
-  'shared-memory/shared-struct-workers': [PASS, ['tsan', SKIP]],
 }],  # variant == stress_incremental_marking
 
 ##############################################################################