Usage in README is misleading to wrong configuration for JetBrains

The sample config in https://github.com/github/github-mcp-server?tab=readme-ov-file#usage-in-other-mcp-hosts won't work in JetBrains.

See: https://github.com/microsoft/copilot-intellij-feedback/issues/354#issuecomment-2994965997

cc @flytiny @hangwan97

