Set proper python-aexpect and python-avocado package stream branches for 82LTS

Signed-off-by: Merlin Mathesius <mmathesi@redhat.com>

avocado.yaml

@@ -6,8 +6,6 @@ data:
   description: >-
     Avocado is a set of tools and libraries (what people call
     these days a framework) to perform automated testing.
-    This is the 'latest' rolling stream that tracks with the
-    most recent upstream release.
   license:
     module:
     - MIT
@@ -53,10 +51,10 @@ data:
     rpms:
       python-aexpect:
         rationale: A python library to control interactive applications needed by avocado
-        ref: latest
+        ref: stable
         buildorder: 10
       python-avocado:
         rationale: Framework with tools and libraries for Automated Testing
-        ref: latest
+        ref: 82lts
         buildorder: 20
 ...