remove mermail render cache

[VoidIsVoid]

Summary

In version 0.13.1, there will be a render bug when render a flowchart in a stream mode response.
This is because chartId in web/app/components/base/mermaid/index.tsx nerver changed when props.PrimitiveCode is different, which made it easy to render the same cache svg by the same chartId.
When props.PrimitiveCode changed, it will create to many cache in localstorage in the middle of stream without a cleaning stratege.
So I made this pr to remove the cache.

Tip

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Screenshots

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Checklist

Important

Please review the checklist below before submitting your pull request.

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods