docs: add disclaimer for roadmap

[ran-huang]

Signed-off-by: Ran huangran.alex@gmail.com

What problem does this PR solve?

Add a disclaimer notice.

Issue Number: close #xxx

Problem Summary:

What is changed and how it works?

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

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

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• bb7133

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[bb7133]

LGTM

[ran-huang]

/merge

[ti-chi-bot]

@ran-huang: /merge is only allowed for the committers, you can assign this pull request to the committer in list by filling /assign @committer in the comment to help merge this pull request.

In response to this:

/merge

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[hawkingrei]

/merge

[ti-chi-bot]

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

Commit hash: 52fcc96

[hawkingrei]

/run-unit-test
/run-build

[sre-bot]

TiDB MergeCI notify

✅ Well Done! New fixed [1] after this pr merged.

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci-tidb/integration-ddl-test	🔴 failed 1, success 5, total 6	25 min	Existing failure
idc-jenkins-ci/integration-cdc-test	✅ all 37 tests passed	27 min	Fixed
idc-jenkins-ci-tidb/integration-common-test	🟢 all 17 tests passed	16 min	Existing passed
idc-jenkins-ci-tidb/common-test	🟢 all 11 tests passed	9 min 47 sec	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	6 min 45 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	5 min 44 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	5 min 37 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	3 min 37 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	3 min 34 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed