gh-35079: Remove 'docker' from the names of the Docker images published on ghcr.io

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### 📚 Description

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We shorten the names of the Docker images generated by our portability
tests slightly by removing the redundant word `docker` from it.
<!-- Why is this change required? What problem does it solve? -->
This is done because the previously used names still belong to the old
repository (which is now renamed as sagemath/sage-archive-...), and the
new repository does not have permissions to push new versions there.
This can be changed package by package in the web interface, but there
is no API for doing so and we have over 1000 packages. So instead we
change the naming pattern; the removal of the redundant word is a
welcome side effect.
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example "Closes #1337" -->

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### ⌛ Dependencies
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URL: #35079
Reported by: Matthias Köppe
Reviewer(s): Dima Pasechnik, Tobias Diez

Author: Release Manager

build/pkgs/configure/checksums.ini

@@ -1,4 +1,4 @@
 tarball=configure-VERSION.tar.gz
-sha1=b9a6c30f4f1c828ca611527d104643d8c0b89ed9
-md5=37a7a99a528efa8a4eea1beff33985db
-cksum=1112286999
+sha1=387297d7e488eb9db6de3ceb80e204d2bdedcfdf
+md5=21203b7dbe667c4633c98139bb1b51fb
+cksum=4016304194

build/pkgs/configure/package-version.txt

@@ -1 +1 @@
-a822a2132aa0e85069ec8b6efa48ad6db08cc044
+96f5cd2fb8aa1a83f1e0ae8112883a64e79031e5

tox.ini

@@ -646,7 +646,7 @@ commands =
     docker-{arm64,armhf}:  docker run --rm --privileged multiarch/qemu-user-static:register --reset
     docker:        bash -c 'if [ x"{env:DOCKER_CONFIG_FILE:}" != x ]; then mkdir -p {envdir}/.docker && ln -sf $(realpath "{env:DOCKER_CONFIG_FILE:}") {envdir}/.docker/; fi'
     docker:        bash -c 'for docker_target in {env:DOCKER_TARGETS:with-targets}; do \
-    docker:            BUILD_IMAGE_STEM=sage-$(echo {envname} | sed s/-incremental//); \
+    docker:            BUILD_IMAGE_STEM=sage-$(echo {envname} | sed "s/docker-//;s/-incremental//"); \
     docker:            BUILD_IMAGE=$DOCKER_PUSH_REPOSITORY$BUILD_IMAGE_STEM-$docker_target; \
     docker:            BUILD_TAG=$(git describe --dirty --always); \
     docker:            TAG_ARGS=$(for tag in $BUILD_TAG {env:EXTRA_DOCKER_TAGS:}; do echo --tag $BUILD_IMAGE:$tag; done); \