Update README

Author: Aaron-Hsieh-0129

docs/api/README.rst

@@ -18,13 +18,11 @@ The following dependencies are required:
 - **nvhpc** 21.3 *(required for GPU usage)* - Installable from the NVIDIA website.
 - **AMGX** 2.4.0 *(required for GPU usage, can be automatically downloaded via CMake)*
 
-  .. note::
+> **Note**  
+> If you encounter errors while downloading AMGX, you may need to specify the NVHPC path and library paths manually.
 
-     If you encounter errors while downloading AMGX, you may need to specify the NVHPC path and library paths manually.
-
-  .. warning::
-
-     If you do **not** want to use GPU, ensure that the `GPU_POISSON` flag in `./src/Config.hpp` is **disabled**.
+> **Warning**  
+> If you do **not** want to use GPU, ensure that the `GPU_POISSON` flag in `./src/Config.hpp` is **disabled**.
 
 Installing dependencies for the first time may take approximately **20 minutes**.