Update installation_en.md

doc/doc_en/installation_en.md

@@ -49,20 +49,7 @@ docker images
 hub.baidubce.com/paddlepaddle/paddle   latest-gpu-cuda9.0-cudnn7-dev    f56310dcc829
 ```
 
-2. Change default version of python3
-
-Python3.5 is used as the default version of python. However, Python3.7 is preferred in PaddleOCR for better compatibility of third-party libraries. After entering docker, you can edit file `/etc/profile`, add the following content at the end of the file.
-
-
-```shell
-
-alias python3=python3.7
-alias pip3=pip3.7
-```
-
-After saving the file `/etc/profile`. The command `source /etc/profile` needs to be carried out to make the default python version as 3.7 effective.
-
-3. Install PaddlePaddle Fluid v1.7 (the higher version is not supported yet, the adaptation work is in progress)
+**2. Install PaddlePaddle Fluid v1.7 (the higher version is not supported yet, the adaptation work is in progress)**
 ```
 pip3 install --upgrade pip
 
@@ -78,7 +65,7 @@ python3 -m pip install paddlepaddle==1.7.2 -i https://pypi.tuna.tsinghua.edu.cn/
 For more software version requirements, please refer to the instructions in [Installation Document](https://www.paddlepaddle.org.cn/install/quick) for operation.
 
 
-4. Clone PaddleOCR repo
+**3. Clone PaddleOCR repo**
 ```
 # Recommend
 git clone https://github.com/PaddlePaddle/PaddleOCR
@@ -90,7 +77,7 @@ git clone https://gitee.com/paddlepaddle/PaddleOCR
 # Note: The cloud-hosting code may not be able to synchronize the update with this GitHub project in real time. There might be a delay of 3-5 days. Please give priority to the recommended method.
 ```
 
-5. Install third-party libraries
+**4. Install third-party libraries**
 ```
 cd PaddleOCR
 pip3 install -r requirments.txt