Updated obsolete faqs (#3575)

### What problem does this PR solve?

### Type of change

- [x] Documentation Update

docker/README.md

@@ -77,7 +77,7 @@ The [.env](./.env) file contains important environment variables for Docker.
   
   - `infiniflow/ragflow:dev-slim` (default): The RAGFlow Docker image without embedding models.  
   - `infiniflow/ragflow:dev`: The RAGFlow Docker image with embedding models including:
-    - Embedded embedding models:
+    - Built-in embedding models:
       - `BAAI/bge-large-zh-v1.5` 
       - `BAAI/bge-reranker-v2-m3`
       - `maidalun1020/bce-embedding-base_v1`
@@ -117,6 +117,11 @@ The [.env](./.env) file contains important environment variables for Docker.
 - `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 128M file size limit.
+
 ## 🐋 Service configuration
 
 [service_conf.yaml](./service_conf.yaml) specifies the system-level configuration for RAGFlow and is used by its API server and task executor. In a dockerized setup, this file is automatically created based on the [service_conf.yaml.template](./service_conf.yaml.template) file (replacing all environment variables by their values).
@@ -154,4 +159,4 @@ The [.env](./.env) file contains important environment variables for Docker.
   - `api_key`: The API key for the specified LLM. You will need to apply for your model API key online.
 
 > [!TIP]  
-> If you do not set the default LLM here, configure the default LLM on the **Settings** page in the RAGFlow UI.
+> If you do not set the default LLM here, configure the default LLM on the **Settings** page in the RAGFlow UI.