Update channels.md to reflect that the latest channel now points …

…to master instead of the testnet (#694)

Update `channels.md` to reflect that the `latest` channel now points to mainnet instead of the testnet.

docs/src/concepts/channels.md

@@ -16,13 +16,9 @@
 
 <!-- This section should give an overview of the latest channel -->
 <!-- latest:example:start -->
-The `latest` channel is pointing to our latest beta network. This toolchain should be used to interact with and build on the latest testnet. This is also the default channel for `fuelup`.
+The `latest` channel is pointing to our mainnet network. This toolchain should be used to interact with and build on mainnet. This is also the default channel for `fuelup`.
 <!-- latest:example:end -->
 
-> **Note**
->
-> The `latest` channel is used to point latest compatible versions of `forc` and `fuel-core`, after version v0.20.0 latest is changed to point to the latest network. This is a breaking change and should be taken into account for existing workflows.
-
 ## The `nightly` channel
 
 <!-- This section should give an overview of the nightly channel -->