Remove package builders for unsupported platforms.

We do not plan to do any more releases on these platforms, and even if
we do they should not need any changes to the package builders, so clean
up the dockerfiles for them.

.github/data/matrices.yaml

@@ -52,8 +52,6 @@ package-builders:
       platforms:
         - linux/amd64
         - linux/arm64/v8
-    - <<: *centos-stream
-      os: centos-stream8
     - os: centos7
       revisions: *pkg-builder-revs
       platforms:
@@ -78,10 +76,6 @@ package-builders:
         - linux/arm64/v8
     - <<: *fedora
       os: fedora39
-    - <<: *fedora
-      os: fedora38
-      revisions:
-        - v1
     - &opensuse
       os: opensusetumbleweed
       revisions: *pkg-builder-revs
@@ -90,10 +84,6 @@ package-builders:
         - linux/arm64/v8
     - <<: *opensuse
       os: opensuse15.5
-    - <<: *opensuse
-      os: opensuse15.4
-      revisions:
-        - v1
     - &oracle
       os: oraclelinux9
       revisions: *pkg-builder-revs
@@ -117,8 +107,6 @@ package-builders:
         - linux/amd64
         - linux/arm/v7
         - linux/arm64/v8
-    - <<: *ubuntu
-      os: ubuntu23.10
     - <<: *ubuntu
       os: ubuntu22.04
     - <<: *ubuntu