Remove all the MOODLE_INTERNAL fixture references

[stronk7]

Coming from #132, as far as moodle-cs is now an standalone product, we don't need these lines, previously required, in all the fixture files:

defined('MOODLE_INTERNAL') || die(); // Make this always the 1st line in all CS fixtures.

(or similar)

This is about to proceed to remove all them, not needed any more.

Note that there may be some MOODLE_INTERNAL uses in fixtures, sniffs and tests that can be legit (for the moodle.Files.MoodleInernal sniff). These need to remain unmodified.

Ciao :-)