image-mirroring: stop mirroring coreos-assembler for releases < 4.12

We don't care about those tags anymore and they should no longer be
used.

Author: jlebon

core-services/image-mirroring/_config.yaml

@@ -679,18 +679,6 @@ supplementalCIImages:
     image: quay.io/coreos-assembler/coreos-assembler:rhcos-4.13
   coreos/coreos-assembler:4.12:
     image: quay.io/coreos-assembler/coreos-assembler:rhcos-4.12
-  coreos/coreos-assembler:4.11:
-    image: quay.io/coreos-assembler/coreos-assembler:rhcos-4.11
-  coreos/coreos-assembler:4.10:
-    image: quay.io/coreos-assembler/coreos-assembler:rhcos-4.10
-  coreos/coreos-assembler:4.9:
-    image: quay.io/coreos-assembler/coreos-assembler:rhcos-4.9
-  coreos/coreos-assembler:4.8:
-    image: quay.io/coreos-assembler/coreos-assembler:rhcos-4.8
-  coreos/coreos-assembler:4.7:
-    image: quay.io/coreos-assembler/coreos-assembler:rhcos-4.7
-  coreos/coreos-assembler:4.6:
-    image: quay.io/coreos-assembler/coreos-assembler:rhcos-4.6
   konveyor/builder:latest:
     image: quay.io/konveyor/builder:latest
   konveyor/builder:ubi9-latest: