build: fix go version in go.mod file

[wuhuizuo]

Why

> go run ./cmd/monitoring.go --tag master --config monitoring.yaml --token <token>
go: updates to go.mod needed; to update it:
	go mod tidy

[ti-chi-bot]

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[wuhuizuo]

/cherry-pick release-8.5

[ti-chi-bot]

@wuhuizuo: once the present PR merges, I will cherry-pick it on top of release-8.5 in the new PR and assign it to you.

In response to this:

/cherry-pick release-8.5

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[wuhuizuo]

/cc @csuzhangxc