docs: make BEDROCK_REGION required for AWS Bedrock integration (#262)

Author: notgiorgi

self-host/customize-deployment/environment-variables.mdx

@@ -255,7 +255,7 @@ To enable AI Analyst, set `AI_COPILOT_ENABLED=true` and provide an API key for `
 | `BEDROCK_ACCESS_KEY_ID`    | AWS access key ID for Bedrock                                 | Required if not using API key                    |                       |
 | `BEDROCK_SECRET_ACCESS_KEY`| AWS secret access key for Bedrock                             | Required if using access key ID                  |                       |
 | `BEDROCK_SESSION_TOKEN`    | AWS session token (for temporary credentials)                 |                                                  |                       |
-| `BEDROCK_REGION`           | AWS region for Bedrock                                        | Required when using IAM credentials              |                       |
+| `BEDROCK_REGION`           | AWS region for Bedrock                                        | <Icon icon="square-check" iconType="solid" />              |                       |
 | `BEDROCK_MODEL_NAME`       | Bedrock model name to use                                     |                                                  | `claude-sonnet-4-5`   |
 | `BEDROCK_EMBEDDING_MODEL`  | Bedrock embedding model for verified answers                  |                                                  | `cohere.embed-english-v3` |
 | `BEDROCK_AVAILABLE_MODELS` | Comma-separated list of models available in the model picker  |                                                  | All supported models  |