docs: correct parameter schema key in Dynamic Servers documentation

[bianbianzhu]

Summary

This PR corrects a documentation typo in the README.md where the update method for a registered tool was incorrectly using the key paramSchema instead of the correct paramsSchema.

Motivation and Context

The MCP SDK's RegisteredTool.update() method expects an object with a paramsSchema key to update the tool's input schema.

Below is the type definition of the update method of RegisteredTool

  update<InputArgs extends ZodRawShape, OutputArgs extends ZodRawShape>(
    updates: {
      name?: string | null,
      title?: string,
      description?: string,
      paramsSchema?: InputArgs,
      outputSchema?: OutputArgs,
      annotations?: ToolAnnotations,
      callback?: ToolCallback<InputArgs>,
      enabled?: boolean
    }): void

How Has This Been Tested?

• Verified the correct key (paramsSchema) is used in the SDK source code (src/server/mcp.ts).
• Confirmed that updating a tool with paramsSchema works as intended in a sample MCP server.
• No code changes were made; this is a documentation-only update.

Breaking Changes

No breaking changes. Doc fix only.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed