=doc#15830 fixed the mismatch between akka-docs and akka API

=doc#15830 fixed the mismatch between akka-docs and akka API

=doc #15830 surrounded the word actor with :class and backticks in order to get it highlighted into documentation
Merge branch 'PiyushMishra#15830-there-is-mismatch-between-akka-docs-and-akka-API' of https://github.com/PiyushMishra/akka into PiyushMishra#15830-there-is-mismatch-between-akka-docs-and-akka-API