regression in #997 : IE8 still needs split test runs to prevent OOM issues.

[romainmenke]

@JakeChampion

I made a mistake in #997
This is why IE8 is failing more frequently now.
Maybe you can include the fix in one of the open PR's?

Otherwise I will open a new PR with the fix later.

fix :

https://github.com/Financial-Times/polyfill-library/blob/df5bab7c91d134ebdfae9edcf4c1626a1f2c3923/test/polyfills/remotetest.js#L167

-!modified.testEverything // no need to shard tests if only a subset is tested
+modified.testEverything // no need to shard tests if only a subset is tested

[romainmenke]

Thank you!