update communication.png in README.

[Alexkun]

What is the purpose of the change

update communication.png in README.

Brief change log

(for example:)

• update communication.png in README

Verifying this change

(Please pick either of the following options)
This change is a trivial rework / code cleanup without any test coverage.
(or)
This change is already covered by existing tests, such as (please describe tests).
(or)
This change added tests and can be verified as follows:
(example:)

• Added tests for creating and execute the Streamis jobs and verify the availability of different Streamis Job, such as flinkSQL, Jar.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (yes / no)
• Anything that affects deployment: (yes / no / don't know)
• The Core framework, i.e., JobManager, Server.: (yes / no)

Documentation

• Does this pull request introduce a new feature? (yes / no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)