Module tests unnecessary strict mode

[rhuanjl]

As module code is always treated as strict mode code (https://tc39.github.io/ecma262/#sec-strict-mode-code) it is unnecessary to emit strict and non-strict versions of tests that are to be run as module code.

This results in longer running times and doubling the failure/pass counts for these tests for no purpose.

I think this could be updated by revising create-scenarios.js to check for test.attrs.flags.module.

[adrianheine]

I'm in favor of this! Do you want to prepare a PR?