bump up python version to 3.12 (#1778)

Per @ezyang 's suggestion.

Let's see if it resolves CI failure
https://github.com/pytorch/torchtitan/actions/runs/18171202123/job/51726096088#step:16:491

Author: tianyu-l

.ci/docker/build.sh

@@ -15,7 +15,7 @@ echo "Building ${IMAGE_NAME} Docker image"
 OS=ubuntu
 OS_VERSION=20.04
 CLANG_VERSION=""
-PYTHON_VERSION=3.11
+PYTHON_VERSION=3.12
 MINICONDA_VERSION=24.3.0-0
 
 case "${IMAGE_NAME}" in

pyproject.toml

@@ -3,7 +3,7 @@
 name = "torchtitan"
 description = "A PyTorch native platform for training generative AI models"
 readme = "README.md"
-requires-python = ">=3.10"
+requires-python = ">=3.12"
 license = {file = "LICENSE"}
 authors = [
     { name = "PyTorch Team", email = "packages@pytorch.org" },