Integration test - change image URL to post-5.3-generated size

[johnwatkins0]

Description of the Change

Before WP 5.3, one of the integration tests for the get_largest_acceptable_image_url method returned a large-size version of a test image. Since 5.3 introduced the new 1536x1536 size to core, the method now returns the image at that size.

This one-line change simply updates the file name to make the test pass.

Benefits

Passing tests.

Verification Process

If the Travis build passes, this update is successful.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.

Applicable Issues

Is applicable to #157 but does not come close to resolving it.

[dinhtungdu]

Look good to me 👌