broken link, window partitions

[jgogstad]

1. Open the main documentation, https://docs.malloydata.dev/documentation/
2. Click "Window Partitions" under experiments, it links to https://docs.malloydata.dev/documentation/experiments/window
3. Observe a blank white page with no contents

Some experimental features are described on the main page for window functions: https://docs.malloydata.dev/documentation/language/calculations_windows#partitioning. Should probably be extracted?