✏ Fix typo in docs about contributing, for compatibility with pip in Zsh (#5523)

Co-authored-by: zhangbo <zhangbo@zjptmc.com>
Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

docs/en/docs/contributing.md

@@ -108,7 +108,7 @@ After activating the environment as described above:
 <div class="termy">
 
 ```console
-$ pip install -e .[dev,doc,test]
+$ pip install -e ."[dev,doc,test]"
 
 ---> 100%
 ```

docs/ja/docs/contributing.md

@@ -97,7 +97,7 @@ $ python -m venv env
 <div class="termy">
 
 ```console
-$ pip install -e .[dev,doc,test]
+$ pip install -e ."[dev,doc,test]"
 
 ---> 100%
 ```

docs/pt/docs/contributing.md

@@ -98,7 +98,7 @@ Após ativar o ambiente como descrito acima:
 <div class="termy">
 
 ```console
-$ pip install -e .[dev,doc,test]
+$ pip install -e ."[dev,doc,test]"
 
 ---> 100%
 ```

docs/zh/docs/contributing.md

@@ -97,7 +97,7 @@ $ python -m venv env
 <div class="termy">
 
 ```console
-$ pip install -e .[dev,doc,test]
+$ pip install -e ."[dev,doc,test]"
 
 ---> 100%
 ```