Rewrite description for URL alias on node/add/*

The current description is not very helpful.

Change the description

Changing the description text

None

None

I am not sure

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Current:
Optionally specify an alternative URL by which this content can be accessed. For example, type "about" when writing an about page. Use a relative path and don't add a trailing slash or the URL alias won't work.

Proposed:
The alternative URL for this content. For example, type "about" when creating an about page. Use a relative path without a trailing slash