Update the prompts to try and generate only JSON (!)

langchain_templates/chat_prompts/initial_template.txt

@@ -10,7 +10,7 @@ Unless explicitly specified with the topic, create about 10 slides.
 {question}
 
 
-The output must be valid and syntactically correct JSON adhering to the following schema:
+The output must be only a valid and syntactically correct JSON adhering to the following schema:
 {{
     "title": "Presentation Title",
     "slides": [

langchain_templates/chat_prompts/refinement_template.txt

@@ -18,7 +18,7 @@ You also fix any syntax error that may be present in the JSON-formatted content.
 {previous_content}
 
 
-The output must be valid and syntactically correct JSON adhering to the following schema:
+The output must be only a valid and syntactically correct JSON adhering to the following schema:
 {{
     "title": "Presentation Title",
     "slides": [