docs: update steps in docs readme (#360)

* docs: update docs readme steps

* fix: Update docs/README.rst

Co-authored-by: Brendan <2bndy5@gmail.com>

---------

Co-authored-by: Brendan <2bndy5@gmail.com>

Author: shenxianpeng

docs/README.rst

@@ -1,23 +1,22 @@
 How to build the docs
 =====================
 
-From the root directory of the repository, do the following to steps
+From the root directory of the repository, do the following in steps
 
 1. Install docs' dependencies
 
    .. code-block:: text
 
-       pip install -r docs/requirements.txt
+       pip install --group 'docs'
 
-   On Linux, you may need to use `pip3` instead.
 
 2. Build the docs
 
    .. code-block:: text
 
        mkdocs build
 
-   or use the following command to see changes rendered in realtime.
+   Or use the following command to see changes rendered in real-time.
 
    .. code-block:: text