Expressions: Set additionalProperties to false in JSON schema

Some backends use grammar constraints that allow additional properties
with the generated JSON schema, resulting in an incoherent and extremely
long JSON.

Set this to false so the model can generate what we need and nothing else.

Signed-off-by: kingbri <8082010+kingbri1@users.noreply.github.com>

public/scripts/extensions/expressions/index.js

@@ -978,6 +978,7 @@ function getJsonSchema(emotions) {
         required: [
             'emotion',
         ],
+        additionalProperties: false,
     };
 }