[turbofan] Disable test that started to timeout.

The two tests in question got a lot slower and started to timeout now
that the C++ fallback implementation of the %Arguments intrinsics is
composable with respect to inlining.

R=bmeurer@chromium.org,machenbach@chromium.org

Review URL: https://codereview.chromium.org/1330203003

Cr-Commit-Position: refs/heads/master@{#30674}

test/mjsunit/mjsunit.status

@@ -75,10 +75,12 @@
   'bit-not': [PASS, NO_VARIANTS],
   'json2': [PASS, NO_VARIANTS],
   'packed-elements': [PASS, NO_VARIANTS],
+  'string-indexof-1': [PASS, NO_VARIANTS],
   'unbox-double-arrays': [PASS, NO_VARIANTS],
   'unicode-test': [PASS, NO_VARIANTS],
   'whitespaces': [PASS, NO_VARIANTS],
   'compiler/osr-assert': [PASS, NO_VARIANTS],
+  'es6/string-fromcodepoint': [PASS, NO_VARIANTS],
   'regress/regress-2185-2': [PASS, NO_VARIANTS],
   'regress/regress-2612': [PASS, NO_VARIANTS],