Update stale comment in test
Update stale comment in test

Summary:
find_js_tests's documentation refers to PHP, but find_js_tests looks for
JavaScript tests, not PHP tests. Update the documentation to reduce
confusion.

This commit should not change behaviour.

Reviewed By: wez

Differential Revision: D8431190

fbshipit-source-id: 3e6e241fd9cbc06137e40a59a763ff6098e35646

wez/watchman,facebook/watchman,facebook/watchman,nodakai/watchman,wez/watchman,wez/watchman,nodakai/watchman,facebook/watchman,nodakai/watchman,nodakai/watchman,facebook/watchman,wez/watchman,wez/watchman,nodakai/watchman,facebook/watchman,facebook/watchman,facebook/watchman,nodakai/watchman,nodakai/watchman,wez/watchman,nodakai/watchman,wez/watchman,wez/watchman,facebook/watchman,nodakai/watchman,facebook/watchman,wez/watchman