grafana(dm): fix grafana expr (#4405)

[ti-chi-bot]

This is an automated cherry-pick of #4405

What problem does this PR solve?

Issue Number: close #4404

What is changed and how it works?

use right expr

• fix standard's lag lable not show
  

• fix binlog file gap between master and syncer
  

• fix binlog file gap between relay and syncer
  

• fix binlog file gap between master and relay
  

Check List

Tests

• Manual test (add detailed scripts or steps below)
• No code

Code changes

Side effects

Related changes

• Need to cherry-pick to the release branch

Release note

`None`.

[ti-chi-bot]

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[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (release-5.3@c13ec95). Click here to learn what that means.
The diff coverage is n/a.

@@               Coverage Diff                @@
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[lance6716]

/assign @nongfushanquan

[lance6716]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: b893ca3

[lance6716]

/run-integration-test