update london demo to point at london3 (#11533)

docs/Demo-Sites.md

@@ -10,7 +10,7 @@ You can also view live demos of Netdata at **[https://www.netdata.cloud](https:/
 
 | Location            | Netdata demo URL                                                                                                                              | 60 mins reqs                                                                                                                                                                                                                                                 | VM donated by                                      |
 | :------------------ | :-------------------------------------------------------------------------------------------------------------------------------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| :------------------------------------------------- |
-| London (UK)         | **[london.my-netdata.io](https://london.my-netdata.io)**<br/>(this is the global Netdata **registry** and has **named** and **mysql** charts) | [![Requests Per Second](https://london.my-netdata.io/api/v1/badge.svg?chart=netdata.requests&dimensions=requests&after=-3600&options=unaligned&group=sum&label=reqs&units=empty&value_color=blue&precision=0&v42)](https://london.my-netdata.io)             | [DigitalOcean.com](https://m.do.co/c/83dc9f941745) |
+| London (UK)         | **[london3.my-netdata.io](https://london3.my-netdata.io)**<br/>(this is the global Netdata **registry** and has **named** and **mysql** charts) | [![Requests Per Second](https://london3.my-netdata.io/api/v1/badge.svg?chart=netdata.requests&dimensions=requests&after=-3600&options=unaligned&group=sum&label=reqs&units=empty&value_color=blue&precision=0&v42)](https://london3.my-netdata.io)             | [DigitalOcean.com](https://m.do.co/c/83dc9f941745) |
 | Atlanta (USA)       | **[cdn77.my-netdata.io](https://cdn77.my-netdata.io)**<br/>(with **named** and **mysql** charts)                                              | [![Requests Per Second](https://cdn77.my-netdata.io/api/v1/badge.svg?chart=netdata.requests&dimensions=requests&after=-3600&options=unaligned&group=sum&label=reqs&units=empty&value_color=blue&precision=0&v42)](https://cdn77.my-netdata.io)               | [CDN77.com](https://www.cdn77.com/)                |
 | Israel              | **[octopuscs.my-netdata.io](https://octopuscs.my-netdata.io)**                                                                                | [![Requests Per Second](https://octopuscs.my-netdata.io/api/v1/badge.svg?chart=netdata.requests&dimensions=requests&after=-3600&options=unaligned&group=sum&label=reqs&units=empty&value_color=blue&precision=0&v42)](https://octopuscs.my-netdata.io)       | [OctopusCS.com](https://www.octopuscs.com)         |
 | Bangalore (India)   | **[bangalore.my-netdata.io](https://bangalore.my-netdata.io)**                                                                                | [![Requests Per Second](https://bangalore.my-netdata.io/api/v1/badge.svg?chart=netdata.requests&dimensions=requests&after=-3600&options=unaligned&group=sum&label=reqs&units=empty&value_color=blue&precision=0&v42)](https://bangalore.my-netdata.io)       | [DigitalOcean.com](https://m.do.co/c/83dc9f941745) |