Update contexts.mdx

Author: lcian

develop-docs/sdk/data-model/event-payloads/contexts.mdx

@@ -801,13 +801,13 @@ This is mostly set on transactions in a web server environment where one transac
 
 : _Optional_. The cookie values. Can be passed, unparsed, as a string, as a dictionary, or as a list of tuples.
 
-- Example: `["PHPSESSID=12345; csrftoken=1234567"]`
+- Example: `{ "PHPSESSID": "12345", "csrftoken": "1234567" }`
 
 `headers`
 
 : _Optional_. A dictionary of submitted headers. If a header appears multiple times it, needs to be merged according to the HTTP standard for header merging. Sentry treats header names as case-insensitive.
 
-- Example: `[["Content-Type", "text/plain"]]`
+- Example: `{ "Content-Type": "text/plain" }`
 
 `status_code`