Remove appdevdocreleases.md

The only document to which this page points is no longer provided. Remove
the page.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>

content/appdevdocreleases.md

-+++
-date = "2016-12-12"
-weight = 100
-
-title = "AppdevDocReleases"
-
-aliases = [
-    "/old-wiki/AppdevDocReleases"
-]
-+++
-
-## Documentation Releases
-
-[16.12](https://appdev.apertis.org/documentation/16.12/)
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