Remove invalid Python variants not present in MCR

Removed Python 3.9 variants (3.9-trixie, 3.9-bookworm, 3.9-bullseye) and
all bullseye variants (3-bullseye, 3.14-bullseye through 3.10-bullseye) from
the python template - these tags do not exist in MCR with the version 3
prefix. Verified all remaining variants across all templates against MCR.

Co-authored-by: Kaniska244 <186041440+Kaniska244@users.noreply.github.com>

Author: Copilot

src/python/devcontainer-template.json

@@ -9,29 +9,20 @@
     "options": {
         "imageVariant": {
             "type": "string",
-            "description": "Python version (use -bookworm, or -bullseye variants on local arm64/Apple Silicon):",
+            "description": "Python version (use -trixie, or -bookworm variants on local arm64/Apple Silicon):",
             "proposals": [
                 "3-trixie",
                 "3.14-trixie",
-                "3.13-trixie",				
+                "3.13-trixie",
                 "3.12-trixie",
                 "3.11-trixie",
                 "3.10-trixie",
-                "3.9-trixie",				
                 "3-bookworm",
                 "3.14-bookworm",
-                "3.13-bookworm",				
+                "3.13-bookworm",
                 "3.12-bookworm",
                 "3.11-bookworm",
-                "3.10-bookworm",
-                "3.9-bookworm",
-                "3-bullseye",
-                "3.14-bullseye",
-                "3.13-bullseye",
-                "3.12-bullseye",
-                "3.11-bullseye",
-                "3.10-bullseye",
-                "3.9-bullseye"
+                "3.10-bookworm"
             ],
             "default": "3.14-trixie"
         }