MINOR: Add language-specific prompt to kapa.ai bot (#46637)

### Rationale for this change

Asks users to specify language when using the kapa.ai bot

### What changes are included in this PR?

Update user instructions

### Are these changes tested?

Nah but I'll build the docs here to look

### Are there any user-facing changes?

Yeah, the instructions

Authored-by: Nic Crane <thisisnic@gmail.com>
Signed-off-by: Nic Crane <thisisnic@gmail.com>

Author: thisisnic

docs/source/_templates/kapa-ai-bot.html

@@ -6,7 +6,7 @@
         data-project-name="Apache Arrow"
         data-project-color="#000000"
         data-project-logo="https://arrow.apache.org/img/arrow-logo_chevrons_white-txt_black-bg.png"
-        data-modal-disclaimer="This is a custom LLM with access to all [Arrow documentation](https://arrow.apache.org/docs/)."
+        data-modal-disclaimer="This is a custom LLM with access to all [Arrow documentation](https://arrow.apache.org/docs/). Please include the language you are using in your question, e.g., Python, C++, Java, R, etc."
         data-consent-required="true" 
         data-consent-screen-disclaimer="By clicking "I agree, let's chat", you consent to the use of the AI assistant in accordance with kapa.ai's [Privacy Policy](https://www.kapa.ai/content/privacy-policy). This service uses reCAPTCHA, which requires your consent to Google's [Privacy Policy](https://policies.google.com/privacy) and [Terms of Service](https://policies.google.com/terms). By proceeding, you explicitly agree to both kapa.ai's and Google's privacy policies."
     ></script>