fix(devcontainer): upgrade Python to match minimal requirements

`alabaster==1.0.0` requires at least Python 3.10, while DevContainer has 3.9

Upgrading to 3.10

Alternative: upgrade to the 3.13 as the latest


Signed-off-by: Grigorii K. Shartsev <me@shgk.me>

.devcontainer/Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.9 as final
+FROM python:3.10 as final
 
 USER root
 
@@ -12,4 +12,4 @@ RUN export DEBIAN_FRONTEND=noninteractive \
     && mv composer.phar /usr/local/bin/composer \
     && npm install svgexport -g \
     && rm -f /tmp/composer-setup.php \
-    && rm -rf /var/lib/apt/lists/*
+    && rm -rf /var/lib/apt/lists/*