Docs improvements (#645)

* fix channels.md

* fix contributing_to_fuelup.md

* fix fuelup_default.rs

* Update fuelup_default.rs

docs/src/concepts/channels.md

@@ -23,7 +23,7 @@ The `latest` channel is pointing to our latest beta network. This toolchain shou
 
 > **Note**
 >
-> The `latest` channel 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 `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
 

docs/src/developer_guide/contributing_to_fuelup.md

@@ -29,7 +29,7 @@ while integration tests involve directly invoking the `fuelup` binary in a sandb
 temporary filesystem.
 
 Note that some integration tests involve installing a toolchain and adding components, which means they
-will fail without internet connection.
+will fail without an internet connection.
 
 Congratulations! You've now got everything setup and are ready to start making contributions.