Issue #1995: Remove old API reference index page.

docs/reference.md

----
-layout: page
-title: API Reference
-permalink: /reference/
----
-
-<!-- MARKER -->
-## [0.42.0](../api/0.42.0/index)
-## [0.41.0](../api/0.41.0/index)
-## [0.40.0](../api/0.40.0/index)
-## [0.39.0](../api/0.39.0/index)
-## [0.38.0](../api/0.38.0/index)
-## [0.37.0](../api/0.37.0/index)
-## [0.36.0](../api/0.36.0/index)
-## [0.35.0](../api/0.35.0/index)
-## [0.34.0](../api/0.34.0/index)
-## [0.33.0](../api/0.33.0/index)
-## [0.32.0](../api/0.32.0/index)
-## [0.31.0](../api/0.31.0/index)
-## [0.30.0](../api/0.30.0/index)
-## [0.29.0](../api/0.29.0/index)
-## [0.28.0](../api/0.28.0/index)
-## [0.27.0](../api/0.27.0/index)
-## [0.26.0](../api/0.26.0/index)