Add pricing note for Elastic Managed LLM (#2022)

Per [this
comment](#1754 (comment)),
this PR adds a pricing note to the Elastic Managed LLM snippet, which is
referenced from the Security, Observability, and Explore and analyze
docs.

Previews:

- [Security AI
Assistant](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/2022/solutions/security/ai/ai-assistant#elastic-managed-llm-security-ai-assistant)
- [Observability AI
Assistant](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/2022/solutions/observability/observability-ai-assistant#elastic-managed-llm-obs-ai-assistant)
- [Explore and analyze > AI
Assistant](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/2022/explore-analyze/ai-assistant#elastic-managed-llm-ai-assistant)

Author: natasha-moore-elastic

solutions/_snippets/elastic-managed-llm.md

@@ -3,3 +3,7 @@
 The Elastic Managed LLM is available out-of-the box; no manual connector setup or API key management is required for initial use. However, you can configure and use a third-party LLM connector, such as OpenAI, Azure, or Amazon Bedrock if you prefer.
 
 To learn more about security and data privacy, refer to the [connector documentation](https://www.elastic.co/docs/reference/kibana/connectors-kibana/elastic-managed-llm) and [download the model card](https://raw.githubusercontent.com/elastic/kibana/refs/heads/main/docs/reference/resources/Elastic_Managed_LLM_model_card.pdf).
+
+:::{important}
+Using the Elastic Managed LLM incurs additional costs. Refer to [{{ecloud}} pricing](https://www.elastic.co/pricing) for more information.
+:::