Use the support page instead of direct links (#15402)

[ti-chi-bot]

This is an automated cherry-pick of #15402

What is changed, added or deleted? (Required)

The right support channel might depend on:

• Region (US, EMEA, China, ASIA)
• Service (TiDB Cloud, On prem)
• Support contract (Enterprise or Community)
• Type of request (Question on Slack, bugreport on GitHub, support on zendesk/jirasd)

So best to link to https://docs.pingcap.com/tidb/stable/support instead.

I have left:

• Links directly to a specific form ( https://support.pingcap.com/hc/en-us/requests/new?ticket_form_id=7800003722519 )
• Links to email ( mailto:[email protected])
• tidb-cloud/*

Maybe we should add a link to email or otherwise reach sales to support.md.

Previous PR: #14648

Which TiDB version(s) do your changes apply to? (Required)

Tips for choosing the affected version(s):

By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions.

• master (the latest development version)
• v7.5 (TiDB 7.5 versions)
• v7.4 (TiDB 7.4 versions)
• v7.3 (TiDB 7.3 versions)
• v7.1 (TiDB 7.1 versions)
• v6.5 (TiDB 6.5 versions)
• v6.1 (TiDB 6.1 versions)
• v5.4 (TiDB 5.4 versions)
• v5.3 (TiDB 5.3 versions)
• v5.2 (TiDB 5.2 versions)
• v5.1 (TiDB 5.1 versions)
• v5.0 (TiDB 5.0 versions)

What is the related PR or file link(s)?

• This PR is translated from:
• Other reference link(s):

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

[ran-huang]

/approve

[ti-chi-bot]

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