Fix Quick Start installing Airflow 3.1.1 instead of the documented version (#74474)

Author: kaxil

airflow-core/docs/start.rst

@@ -28,7 +28,7 @@ This quick start guide will help you bootstrap an Airflow standalone instance on
 
    Officially supported installation methods are ``pip`` or ``uv``.
 
-   Run ``pip install apache-airflow[EXTRAS]==AIRFLOW_VERSION --constraint "https://raw.githubusercontent.com/apache/airflow/constraints-AIRFLOW_VERSION/constraints-PYTHON_VERSION.txt"``, for example ``pip install "apache-airflow[celery]==3.0.0" --constraint "https://raw.githubusercontent.com/apache/airflow/constraints-3.0.0/constraints-3.11.txt"`` to install Airflow in a reproducible way. You can also use - much faster - ``uv`` - by adding ``uv`` before the command.
+   Run ``pip install apache-airflow[EXTRAS]==AIRFLOW_VERSION --constraint "https://raw.githubusercontent.com/apache/airflow/constraints-AIRFLOW_VERSION/constraints-PYTHON_VERSION.txt"``, for example :subst-code:`pip install "apache-airflow[celery]==|version|" --constraint "https://raw.githubusercontent.com/apache/airflow/constraints-|version|/constraints-3.11.txt"` to install Airflow in a reproducible way. You can also use - much faster - ``uv`` - by adding ``uv`` before the command.
 
 
 
@@ -73,6 +73,7 @@ externally managed environments (PEP 668), so use a virtual environment
 before running ``pip install`` commands:
 
 .. code-block:: bash
+   :substitutions:
 
    # For Windows after WSL2 install, restart computer, then in WSL Ubuntu terminal
    sudo apt update
@@ -95,7 +96,7 @@ before running ``pip install`` commands:
    pip install --upgrade pip
 
    # Install Airflow with correct Python version constraints
-   pip install apache-airflow[celery]==3.1.0 --constraint https://raw.githubusercontent.com/apache/airflow/constraints-3.1.0/constraints-3.12.txt
+   pip install apache-airflow[celery]==|version| --constraint https://raw.githubusercontent.com/apache/airflow/constraints-|version|/constraints-3.12.txt
 
    # Verify installation
    airflow version
@@ -106,14 +107,14 @@ before running ``pip install`` commands:
       :substitutions:
 
 
-      AIRFLOW_VERSION=3.1.1
+      AIRFLOW_VERSION=|version|
 
       # Extract the version of Python you have installed. If you're currently using a Python version that is not supported by Airflow, you may want to set this manually.
       # See above for supported versions.
       PYTHON_VERSION="$(python -c 'import sys; print(f"{sys.version_info.major}.{sys.version_info.minor}")')"
 
       CONSTRAINT_URL="https://raw.githubusercontent.com/apache/airflow/constraints-${AIRFLOW_VERSION}/constraints-${PYTHON_VERSION}.txt"
-      # For example this would install 3.1.1 with python 3.11: https://raw.githubusercontent.com/apache/airflow/constraints-|version|/constraints-3.11.txt
+      # For example this would install |version| with python 3.11: https://raw.githubusercontent.com/apache/airflow/constraints-|version|/constraints-3.11.txt
 
       uv pip install "apache-airflow==${AIRFLOW_VERSION}" --constraint "${CONSTRAINT_URL}"