Do not distribute ajax-loader.gif

[PhilETaylor]

This is a file Joomla doesn't need to be distributing as it deletes it immediately after installing anyway

Part of #22219

[infograf768]

I guess this can be merged on review.
@mbabker @wilsonge

[brianteeman]

This is file is being used. The error is that it shouldnt be in the script of files to remove.

joomla-cms/administrator/modules/mod_sampledata/tmpl/default.php

Line 22 in 4b6a807

modSampledataIconProgress = "' . JUri::root(true) . '/media/jui/img/ajax-loader.gif";

[mbabker]

We still need to take it off the delete array as we have no idea if this loader graphic is being used in extensions. For 4.0 we can make sure we're only shipping one graphic.