build(devcontainer): 调整 pnpm LTS 版本配置时机

将 `pnpm env use lts --global` 命令从 Dockerfile 和 postCreateCommand 中移除，
并在 devcontainer.json 的 onCreateCommand 阶段添加该命令

[skip ci]

.devcontainer/Dockerfile

@@ -96,5 +96,4 @@ RUN sh -c "$(curl -L -o - https://github.com/deluan/zsh-in-docker/releases/downl
 RUN wget -qO- https://get.pnpm.io/install.sh | ENV="$HOME/.zshrc" SHELL="$(which zsh)" zsh - \
     && pnpm --version \
     # /home/usr_vscode/.config/pnpm/rc
-    && pnpm config --global set store-dir /home/usr_vscode/.pnpm-store \
-    && pnpm env use lts --global
+    && pnpm config --global set store-dir /home/usr_vscode/.pnpm-store