Make PHPUnit tests pass locally

[kienstra]

Before, npm run test:phpunit failed locally with:

Time: 8.71 seconds, Memory: 44.50 MB

There was 1 failure:

1) PatternManager\PatternDataHandlers\PatternDataHandlersTest::test_tree_shake_theme_images
Failed asserting that two arrays are identical.
--- Expected
+++ Actual
@@ @@
-Array &0 (
-    0 => '/var/www/html/wp-content/plugins/pattern-manager/wp-modules/pattern-data-handlers/tests/fixtures/patterns/images/used.jpg'
-)
+Array &0 ()

/var/www/html/wp-content/plugins/pattern-manager/wp-modules/pattern-data-handlers/tests/PatternDataHandlersTest.php:198

This is because preg_match() failed on the test pattern:

<!-- wp:image -->
<figure class="wp-block-image size-large"><img src="/wordpress-phpunit/includes/../data/themedir1/default/patterns/images/used.jpg" alt="Cup of tea"/></figure>
<!-- /wp:image -->

In that pattern, get_stylesheet_directory_uri() didn't have http:

/wordpress-phpunit/includes/../data/themedir1/default/

…so preg_match() failed.

This PR filters get_theme_directory_uri() so it starts with https://

How to test

Not needed. But if you want to:

1. npm run test:phpunit
2. Expected: it passes

[kienstra]

Sorry for ignoring this failed test.

This should fix it.

[kienstra]

Thanks so much, @dreamwhisper!