test_pthread_create_standalone is flakey on CI

[kripken]

It doesn't seem to flake locally for some reason. But it flakes on github CI sometimes, and chromium CI quite often.

[sbc100]

Seems like it could be related to the node version being out of date on emscripten-releases. emsdk is 14.18.2 and emscripten-releases is 14.15.5.

[sbc100]

@dschuff said he to would take care of the node update. in the meantime disabling the test seems fine.