fix: proper URL links from README.md to 'Java Dependencies', 'Java MCP Client', 'Java MCP Server' pages

[sleepytomcat]

Motivation and Context

Currently, 'Java Dependencies', 'Java MCP Client', 'Java MCP Server' links from the project's README.md lead to "404" page instead of the expected documentation pages. This PR fixes the links, pointing to the relevant documentation pages hosted at https://java.sdk.modelcontextprotocol.io

How Has This Been Tested?

Tested manually by clicking the fixed links, and observing that the relevant documentation page is indeed loaded into the web browser.

Breaking Changes

There's no breaking changes.

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
• [N/A] My code follows the repository's style guidelines
• [N/A] New and existing tests pass locally
• [N/A] I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

None.