Update the example in module net.box

[xuniq]

Resolves #2271

Deploy: https://docs.d.tarantool.io/en/doc/gh-2271-netbox-example/how-to/getting_started_net_box/

[p7nov]

Nice!
Some comments from my side.

[xuniq]

In the old example, the net.box methods were wrapped in the example() function. That function looked redundant. So, the example has been rewritten and moved to the how-to chapter as an introductory net.box tutorial:
https://docs.d.tarantool.io/en/doc/gh-2271-netbox-example/how-to/getting_started_net_box/