CHANGELOG.md: Update for 23.11rc2

[nepet]

Update changelog and py versions for second release candidate that includes mainly some tests for cln-rest

[endothermicdev]

the changed section should include the cln prefix added to clnrest config options. The full changes are:

config option `rest-certs` changed to `clnrest-certs`
config option `rest-protocol` changed to `clnrest-protocol`
config option `rest-host` changed to `clnrest-host`
config option `rest-port` changed to `clnrest-port`
config option `rest-cors-origins` changed to `clnrest-cors-origins`
config option `rest-csp` changed to `clnrest-csp`

Could probably be summarized in a single line as
clnrest config options rest-certs, rest-protocol, rest-host, rest-port, rest-cors-origins, rest-csp are all now prefixed with cln in order to avoid clashing with c-lightning-REST. (i.e., rest-port to clnrest-port) ([#6857])

[endothermicdev]

Is incrementing the pyln versioning necessary for rc2? I might prefer leaving them as 23.11 for simplicity.

[nepet]

Thanks for your feedback @endothermicdev. I'll work it in and let you know once I am done!

[endothermicdev]

ACK 749b694

[nepet]

Added #6876

[nepet]

Added #6840 to the release candidate.