XWIKI-11177 : Don't display the "Create a new wiki" link for users witho...

Don't display the "Create a new wiki" link for users without the right to create a wiki
Same comment as on https://github.com/xwiki/xwiki-enterprise/pull/61 , ``$hasCreateWiki`` can be overwritten before the macro is called. But it's fine because the create wiki right is also checked when the wiki is created.