docs: update the workflow img and fix the broken slack link

[SparkYuan]

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[coveralls]

Pull Request Test Coverage Report for Build 8092400439

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 (-0.04%) to 74.195%

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Files with Coverage Reduction	New Missed Lines	%
pkg/engine/operation/parser/parser.go	3	79.27%
pkg/engine/operation/parser/spec_parser.go	4	56.1%

Totals
Change from base Build 8092062166:	-0.04%
Covered Lines:	6866
Relevant Lines:	9254

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💛 - Coveralls