Run some slow tail call tests only for fast configurations.

NOTRY=true

Review URL: https://codereview.chromium.org/1822683002

Cr-Commit-Position: refs/heads/master@{#34935}

test/mjsunit/mjsunit.status

@@ -264,6 +264,7 @@
   'readonly': [PASS, SLOW],
   'regress/regress-1200351': [PASS, ['mode == debug', SLOW]],
   'regress/regress-crbug-474297': [PASS, ['mode == debug', SLOW]],
+  'es6/tail-call-megatest*': [PASS, FAST_VARIANTS],
 
   # TODO(titzer): correct WASM adapter frame alignment on arm64
   'wasm/*': [PASS, ['arch == arm64', SKIP]],