fix(dataEvents): widen event metadata typing in stable spec too

Apply the same additionalProperties: true widening to the stable
(2.14) override so stable-namespace data event types are also generated
as an unconstrained map, not Record<string, string>.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: pkubicki

fern/openapi-overrides.yml

@@ -1418,8 +1418,7 @@ components:
             metadata:
               type: object
               description: Optional metadata about the event.
-              additionalProperties:
-                type: string
+              additionalProperties: true
               example:
                 invite_code: ADDAFRIEND
           required:
@@ -1451,8 +1450,7 @@ components:
             metadata:
               type: object
               description: Optional metadata about the event.
-              additionalProperties:
-                type: string
+              additionalProperties: true
               example:
                 invite_code: ADDAFRIEND
           required:
@@ -1486,8 +1484,7 @@ components:
             metadata:
               type: object
               description: Optional metadata about the event.
-              additionalProperties:
-                type: string
+              additionalProperties: true
               example:
                 invite_code: ADDAFRIEND
           required:
@@ -1886,6 +1883,9 @@ components:
             - collection
             - section
     data_event:
+      properties:
+        metadata:
+          additionalProperties: true
       required:
         - type
         - event_name