channels/stable-4.8: Remove filter to include 4.7.z

Generated with:

  $ sed -i '/^  filter: /d' channels/stable-4.8.yaml
  $ hack/stabilization-changes.py

but using the still-in-flight version of that script from [1] to
include the promotions in this commit, so the stabilization bot
doesn't follow up with a whole bunch of parallel promotion pull
requests.

We've been cooking in fast-4.8 long enough that we feel fairly
confident that major 4.7 -> 4.8 issues will have surfaced by now.

[1]: openshift#1039

channels/stable-4.8.yaml

@@ -1,9 +1,36 @@
 feeder:
   delay: PT96H
-  filter: 4\.8\.[0-9]+(.*hotfix.*)?
   name: fast-4.8
 name: stable-4.8
 versions:
+- 4.7.0
+- 4.7.1
+- 4.7.2
+- 4.7.3
+- 4.7.4
+- 4.7.5
+- 4.7.6
+- 4.7.7
+- 4.7.8
+- 4.7.9
+- 4.7.10
+- 4.7.11
+- 4.7.12
+- 4.7.13
+- 4.7.14
+- 4.7.15
+- 4.7.16
+- 4.7.17
+- 4.7.18
+- 4.7.19
+- 4.7.20
+- 4.7.21
+- 4.7.22
+- 4.7.23
+- 4.7.24
+- 4.7.28
+- 4.7.29
+- 4.7.30
 - 4.8.2
 - 4.8.3
 - 4.8.4