MDL-64737 privacy: Fix privacy provider testsuite file names

Only files ending with "_test.php" suffix are implicit part of a
testsuite. So these two were not actually executed.

diff --git a/lib/editor/atto/tests/privacy_provider.php b/lib/editor/atto/tests/privacy_provider_test.php
similarity index 100%
rename from lib/editor/atto/tests/privacy_provider.php
rename to lib/editor/atto/tests/privacy_provider_test.php

diff --git a/lib/userkey/tests/privacy_provider.php b/lib/userkey/tests/privacy_provider_test.php
similarity index 100%
rename from lib/userkey/tests/privacy_provider.php
rename to lib/userkey/tests/privacy_provider_test.php