docs: add -p mcp-client-examples to cargo run commands in clients/README.md

[dj707chen]

Add -p mcp-client-examples to cargo run commands in examples/clients/README.md to fix errors like:

error: no example target named `clients_everything_stdio` in default-run packages

Motivation and Context

When I ran command as examples/clients/README.md:

cargo runcargo run --example clients_everything_stdio

I got errors like:

error: no example target named `clients_everything_stdio` in default-run packages

How Has This Been Tested?

Run the new commands.

Breaking Changes

None.

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

Additional context

[dj707chen]

Opened by mistake, replaced by #592