server: remove unused status api (4.0)

[morgo]

What problem does this PR solve?

The /debug/sub-optimal-plan is unused, undocumented and should be removed.

What is changed and how it works?

What's Changed:

Remove undocumented API.

Check List

Tests

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

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

The undocumented `/debug/sub-optimal-plan`  HTTP API has been removed.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• AilinKid
• djshow832

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[bb7133]

/merge

[ti-chi-bot]

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

Commit hash: c337ae8