Fix typo in about/index.md AR

[celyes]

Fixed the term "blocking call" to "non-blocking call" in about/index.md:41
@Aissaoui-Ahmed@interstellarClub

[fhemberger]

blocking is correct here, see https://nodejs.org/en/about/:

Typically behavior is defined through callbacks at the beginning of a script and at the end starts a server through a blocking call like EventMachine::run(). In Node there is no such start-the-event-loop call.

[celyes]

ok, Corrected the mistake.
@fhemberger

[ghost]

@celyes：You don't need to close it if you had a force push and fixed it, this could be also merged if possible :)

[celyes]

@Maledong : thank you, but it's basically blank lines, so i don't think it deserves to be merged IMO.