Revert "Include experimental in "all" config contexts"

This reverts commit e4b6004183fc4fe8b8b10000c700cdb4613b528d.

src/annotator/config/index.js

@@ -61,14 +61,7 @@ function configurationKeys(appContext) {
       return contexts.notebook;
     case 'all':
       // Complete list of configuration keys used for testing.
-      return [
-        ...contexts.annotator,
-        ...contexts.sidebar,
-        ...contexts.notebook,
-        // "experimental" currently has no uses in any app contexts, but is included
-        // for test coverage
-        'experimental',
-      ];
+      return [...contexts.annotator, ...contexts.sidebar, ...contexts.notebook];
     default:
       throw new Error(`Invalid application context used: "${appContext}"`);
   }