docs: update clickhouse-backup docker args example

[christopherdeutsch]

Hi! I think one of the examples can be simplified.

The current command in the example for clickhouse-backup is

 command:
    - bash
    - -xc
    - "/bin/clickhouse-backup server"

And the Dockerfile ends with:

ENTRYPOINT ["/entrypoint.sh"]
CMD [ "/bin/clickhouse-backup", "--help" ]

This PR will update the docs to just pass server to the entrypoint script, since bash is unnecessary. The -xc flags could be useful for debugging, but I propose that using the args to specify server makes the example more clear.

[Slach]

thanks for contribution

[coveralls]

Pull Request Test Coverage Report for Build 10720629068

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall first build on deutsch/example_docker_args at 65.757%

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Totals
Change from base Build 10720587739:	65.8%
Covered Lines:	8816
Relevant Lines:	13407

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💛 - Coveralls