[test] Shorten regression-*.js filenames to regress-*.js

R=rossberg@chromium.org

Bug: 
Change-Id: Icac33dc87dd660173e5a45d02b31be46f7d1cb2d
Reviewed-on: https://chromium-review.googlesource.com/721550
Commit-Queue: Ben Titzer <titzer@chromium.org>
Reviewed-by: Andreas Rossberg <rossberg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48632}

test/mjsunit/mjsunit.status

@@ -172,7 +172,7 @@
   'regress/regress-599717': [PASS, ['tsan', SKIP]],
 
   # BUG(v8:6924). The test uses a lot of memory.
-  'regress/wasm/regression-694433': [PASS, ['tsan', SKIP]],
+  'regress/wasm/regress-694433': [PASS, ['tsan', SKIP]],
 
   # TODO(bmeurer): Flaky timeouts (sometimes <1s, sometimes >3m).
   'unicodelctest': [PASS, NO_VARIANTS],