update README.md.

Signed-off-by: 葛峻恺 <202115006@mail.sdu.edu.cn>

README.md

@@ -90,7 +90,7 @@ GPR-SIDL-inv/
 Please select the appropriate device according to your requirements. We conducted tests on a Dell laptop with an Intel(R) Core (TM) i7-12700H CPU (maximum physical memory of 15.7 GiB.) and an NVIDIA RTX 3070 Ti Laptop GPU (maximum physical memory of 7.8 GiB).
 
 
-### 📚 Software requirements
+## 📚 Software requirements
 
 No external software. Python dependencies are listed in the requirements.txt.