Fix typos in documentation

[oglok]

fix a typo

[github-actions]

CLA Assistant Lite bot:
Thank you for your submission, we really appreciate it. Like many open-source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution. You can sign the CLA by just posting a Pull Request Comment same as the below format.

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I have read the CLA Document and I hereby sign the CLA

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[ruquanzhao]

Hi @oglok, great work on this contribution! 🙌
To proceed with merging into master, could you please sign the Contributor License Agreement (CLA)? This is a standard step for all contributors.

[coveralls]

Pull Request Test Coverage Report for Build 20605712536

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 7 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.01%) to 46.331%

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Files with Coverage Reduction	New Missed Lines	%
pkg/engine/operation/parser/parser.go	3	74.16%
pkg/engine/operation/parser/spec_parser.go	4	56.1%

Totals
Change from base Build 16158708775:	-0.01%
Covered Lines:	11377
Relevant Lines:	24556

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💛 - Coveralls