Improve RAK7240 docs

[i3mSuperMan]

Summary

Improve documentation of RAK7240 guide, as The Things Stack supports TLS server authentication and client token authentication mode. Whereas the Connect RAK7240 in Basic Station Mode documentation mentioned with a TLS server authentication. Ref: https://www.thethingsindustries.com/docs/gateways/rak-7240/bs/

What is missing? What do you want to see?

• Modify the authentication mode information to TLS server authentication and client token in the documentation.

  This guide will help you set up the RAK2470 gateway to communicate over The Things Stack.

• Modify Gateway Model from RAK2470 to RAK7240 in the above sentence.

  Note: Configuring and connecting RAK7249 and RAK7258 gateways to The Things Stack should be identical as for the RAK7240.

• Added RAK7268 to the above Note point as its configuration is identical with the RAK7240

How do you propose to document this?

Changing above in the documentation. Ref: https://www.thethingsindustries.com/docs/gateways/rak-7240/bs/

Can you do this yourself and submit a Pull Request?

Yes

[i3mSuperMan]

Closes: https://github.com/TheThingsIndustries/lorawan-stack-docs/pull/457