Update hoisted_class_prefix docs with the new "schema" change (#1156

)

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> [!IMPORTANT]
> Update `output-format.mdx` to reflect change in default render message
word from "schema" to "interface" for hoisted classes.
> 
>   - **Documentation Update**:
> - In `output-format.mdx`, updated the description of
`hoisted_class_prefix` to reflect the change in default render message
word from "schema" to "interface".
> - Updated example in `output-format.mdx` to use "interface" instead of
"schema" in the rendered prompt.
> 
> <sup>This description was created by </sup>[<img alt="Ellipsis"
src="https://img.shields.io/badge/Ellipsis-blue?color=175173">](https://www.ellipsis.dev?ref=BoundaryML%2Fbaml&utm_source=github&utm_medium=referral)<sup>
for 0f56dcf. It will automatically
update as commits are pushed.</sup>

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fern/03-reference/baml/prompt-syntax/output-format.mdx

@@ -127,7 +127,15 @@ You can always set it to ` | ` or something else for a specific model you use.
 Prefix of hoisted classes in the prompt. **Default: `<none>`**
 
 Recursive classes are hoisted in the prompt so that any class field can
-reference them using their name.
+reference them using their name. This parameter controls the prefix used for
+hoisted classes as well as the word used in the render message to refer to the
+output type, which defaults to `"schema"`:
+
+```
+Answer in JSON using this schema:
+```
+
+See examples below.
 
 **Recursive BAML Prompt Example**
 
@@ -176,7 +184,7 @@ interface Node {
   next: Node or null
 }
 
-Answer in JSON using this schema:
+Answer in JSON using this interface:
 {
   head: Node or null,
   len: int