docs-md: Delete (obsoleted by docs/)

This was just a prototype start at markdown docs that I never picked
back up.  Now that we have the Markdown/mkdocs done, delete this.

docs-md/atomic-upgrades.md

@@ -1,12 +0,0 @@
-Atomic upgrades and rollback
-----------------------------
-
-Traditional package managers operate "live" on the running system.
-This means it's possible for interrupted updates to result in a
-half-updated system.  This model also makes it significantly harder to
-support rollbacks when updates fail.
-
-In contrast, OSTree always creates a *new* root whenever it's
-performing an update.  This new root shares storage via hardlinks with
-the current system.  Upon success, the bootloader configuration will
-be updated.