Use RFC Documentation Prefixes for all examples

### Existing documentation URL(s)

https://developers.cloudflare.com/magic-transit/reference/bandwidth-measurement/#cloudflare-originated-traffic

### What changes are you suggesting?

It does not make sense to use a non-routable prefix (10.0.1.0/24) as an example prefix that was onboarded to Magic Transit which is only for Public IP prefixes. There are already specific reserved prefixes that can be used for documentation:

https://datatracker.ietf.org/doc/html/rfc5737
IPv4 Documentation Prefixes
The official standards for IPv4 documentation are outlined in RFC 5737. IANA has reserved three specific blocks for these examples:

TEST-NET-1: 192.0.2.0/24
TEST-NET-2: 198.51.100.0/24
TEST-NET-3: 203.0.113.0/24

### Additional information

_No response_