poe: enable reasoning for gpt-oss-120b-cs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: fhennerkes

providers/poe/models/cerebras/gpt-oss-120b-cs.toml

@@ -2,7 +2,7 @@ name = "GPT-OSS-120B-CS"
 release_date = "2025-08-06"
 last_updated = "2025-08-06"
 attachment = true
-reasoning = false
+reasoning = true
 temperature = false
 open_weights = false
 tool_call = true