Update document: how upload file large than 128MB (#3791)

### What problem does this PR solve?

As title.

### Type of change

- [x] Documentation Update

---------

Signed-off-by: Jin Hai <[email protected]>
Co-authored-by: writinwaters <[email protected]>

docker/README.md

@@ -115,12 +115,12 @@ The [.env](./.env) file contains important environment variables for Docker.
 ### MacOS
 
 - `MACOS`  
-  Optimizations for MacOS. It is disabled by default. You can uncomment this line if your OS is MacOS.
+  Optimizations for macOS. It is disabled by default. You can uncomment this line if your OS is macOS.
 
 ### Maximum file size
 
 - `MAX_CONTENT_LENGTH`  
-  The maximum file size for each uploaded file, in bytes. You can uncomment this line if you wish to change the 128M file size limit.
+  The maximum file size for each uploaded file, in bytes. You can uncomment this line if you wish to change the 128M file size limit.  Please also update `client_max_body_size` in nginx/nginx.conf correspondingly.
 
 ## 🐋 Service configuration
 

docs/references/faq.md

@@ -331,14 +331,13 @@ Ensure that you update the **MAX_CONTENT_LENGTH** environment variable:
 1. In **ragflow/docker/.env**, uncomment environment variable `MAX_CONTENT_LENGTH`:
 
    ```
-   MAX_CONTENT_LENGTH=128000000
+   MAX_CONTENT_LENGTH=176160768 # 168MB
    ```
 
-2. Update **docker-compose.yml**:
+2. Update **ragflow/docker/nginx/nginx.conf**:
 
    ```
-   environment:
-     - MAX_CONTENT_LENGTH=${MAX_CONTENT_LENGTH}
+   client_max_body_size 168M
    ```
 
 3. Restart the RAGFlow server: