Update getting_started_retrieval.md

docs/en/tutorials/getting_started_retrieval.md

 # Quick Start
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-At first，please take a reference to [Installation Guide](./install_en.md)to prepare your environment.
+At first，please take a reference to [Installation Guide](./install_en.md) to prepare your environment.
 
 PaddleClas image retrieval supports the following training/evaluation environments:
 ```shell