Remove use of `perflab_aea_get_resource_file_size()`

## Bug Description

When `wp_filesize()` function implemented in Performance plugin by marging this PR #376.  We should remove `perflab_aea_get_resource_file_size()` function as it return result of `wp_filesize()` function so instead of `perflab_aea_get_resource_file_size()` we will use `wp_filesize()` function.