Remove unnecessary transport requires

[koic]

Motivation and Context

The transports are already required by require 'mcp': https://github.com/modelcontextprotocol/ruby-sdk/blob/v0.3.0/lib/mcp.rb#L16-L17

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