branches.yml: drop all branch definitions, keeping only stable

- This is an adjustment for our new topic-based iteration system.
- Do not ship this update until the new iteration system commences.

branches.yml

@@ -1,39 +1,4 @@
 stable:
-    desc: Contains tested patch-release updates, security fixes, and general bug fixes.
+    desc: Contains tested updates, security fixes, and general bug fixes.
     suites:
         - stable
-stable-proposed:
-    desc: Contains work-in-progress stable-branch updates awaiting further testing.
-    suites:
-        - stable-proposed
-        - stable
-testing:
-    desc: Contains major version updates with limited testing.
-    suites:
-        - testing
-        - stable-proposed
-        - stable
-        - rckernel
-testing-proposed:
-    desc: Contains work-in-progress testing-branch updates awaiting further testing.
-    suites:
-        - testing-proposed
-        - testing
-        - stable-proposed
-        - stable
-        - rckernel
-explosive:
-    desc: "** DO NOT USE ** Contains immediate updates reflecting newest packaging Git changes, no human testing conducted and highly experimental."
-    suites:
-        - explosive
-        - testing-proposed
-        - testing
-        - stable-proposed
-        - stable
-        - rckernel
-rckernel:
-    desc: Contains Release Candidate Linux Kernels (and tools) as future Stable-branch updates.
-    suites:
-        - stable-proposed
-        - stable
-        - rckernel