tox.ini: Fix up

Author: Matthias Koeppe

tox.ini

@@ -647,7 +647,7 @@ 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/-docker//;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); \