Wrong command to activate virtual environment in Windows

**Describe the issue**:
According to the [readme](https://github.com/Azure-Samples/llama-index-python?tab=readme-ov-file#using-the-template-locally) , an error occurred when running the following command, the Windows environment does not support running this command.

**Environment**:

- azd version 1.9.5 (commit cd2b7af9995d358aab33c782614f801ac1997dde)
- OS: Windows

**Suggestions**:
Add command to activate the virtual environment on Windows.

**Expected Behavior**:
Successfully activated the virtual environment on windows.

@jongio and @marlenezw for notification.

从 README 的 "Using the template locally" 部分开始，将其中的虚拟环境激活命令与 issue 中描述的 Windows 环境进行比较。使用与 Windows 兼容的命令更新说明，然后验证文档中的命令是否能在 Windows 上成功激活虚拟环境。

由索引模型根据 Issue 内容生成。