Updated default index.html placeholders with disclaimer

Updated Centmin Mod 123.09beta01 main hostname default nginx index.html page and default nginx vhost index.html place holder pages to add a disclaimer for visitors.

• Beta Branch - update main hostname default index.html template
• Beta Branch - Add disclaimer to default index.html placeholder pages

The disclaimer reads as follows:

This was added as some visitors visiting sites which are powered by Centmin Mod LEMP stack are hitting these pages and confusing site ownership thinking that the sites are run by Centmin Mod when they are in fact run by users who downloaded and installed Centmin Mod to power their web sites.

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