sagemathgh-36534: CI Linux: Fix `centos-7` after sagemath#36435, remove `gentoo-python3.12` for now, use `conda-forge` with `-python3.11`
    
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As part of the changes in sagemath#36435, we switched from http to https for
downloading mirror_list.
This broke centos-7; here we fix it.

gentoo-python3.12 was activated a little bit too early. We remove it to
clean up the portability CI workflow.

conda-forge defaults to 3.12 already, and we're not ready for it.

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URL: sagemath#36534
Reported by: Matthias Köppe
Reviewer(s): Kwankyu Lee

Author: Release Manager

.github/workflows/docker.yml

@@ -51,14 +51,13 @@ on:
            "almalinux-9-python3.11",
            "gentoo-python3.10",
            "gentoo-python3.11",
-           "gentoo-python3.12",
            "archlinux-latest",
            "opensuse-15.3-gcc_11-python3.9",
            "opensuse-15.4-gcc_11-python3.10",
            "opensuse-15.5-gcc_11-python3.11",
            "opensuse-tumbleweed-python3.10",
            "opensuse-tumbleweed",
-           "conda-forge",
+           "conda-forge-python3.11",
            "ubuntu-bionic-gcc_8-i386",
            "debian-bullseye-i386",
            ]

build/pkgs/_python3.10/distros/conda.txt

@@ -0,0 +1 @@
+python==3.10

build/pkgs/_python3.11/distros/conda.txt

@@ -0,0 +1 @@
+python==3.11

build/pkgs/_python3.12/distros/conda.txt

@@ -0,0 +1 @@
+python==3.12

build/pkgs/_python3.9/distros/conda.txt

@@ -0,0 +1 @@
+python==3.9

tox.ini

@@ -308,6 +308,7 @@ setenv =
     centos:         BASE_IMAGE=centos
     centos:                                    IGNORE_MISSING_SYSTEM_PACKAGES=yes
     centos-7:         BASE_TAG=centos7
+    centos-7:           BOOTSTRAP=sed -i.bak s/https/http/ .upstream.d/*mirror_list; ./bootstrap
     centos-stream:  BASE_IMAGE=quay.io/centos/centos
     centos-stream:    BASE_TAG=stream
     centos-stream-8:  BASE_TAG=stream8