Only organize Python imports automatically

It's causing changes that aren't reproduced/picked up by prettier:

https://github.com/ankitects/anki/pull/1862#discussion_r870395750

.vscode/settings.json

@@ -1,7 +1,9 @@
 {
     "editor.formatOnSave": true,
+    "[python]": {
         "editor.codeActionsOnSave": {
             "source.organizeImports": true
+        }
     },
     "files.watcherExclude": {
         "**/.git/objects/**": true,