Fix README markdown: add missing code fence and remove extra backticks (#104)

Agent-Logs-Url: https://github.com/SculptAI/GIMBench/sessions/4bd8f7b4-99a8-4b17-b434-011e04d8c22d

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Ki-Seki <60967965+Ki-Seki@users.noreply.github.com>

Author: Copilot

README.md

@@ -83,6 +83,7 @@ python -m gimbench.code.humaneval_infilling \
     --model_name meta-llama/Llama-3.1-8B-Instruct \
     --base_url http://localhost:8000/v1 \
     --no_gimkit
+```
 
 Run SciERC relation extraction benchmark (Hugging Face dataset):
 
@@ -110,7 +111,6 @@ python benchmarks/GIMBench-sci-erc/1_build_dataset.py \
     --repo_id Sculpt-AI/GIMBench-sci-erc \
     --push_to_hub
 ```
-```
 
 ## Development