"""Remove a function definition from the source code.

This function parses the provided source code and removes the definition of the specified function. 
If the function is found, it removes the entire block of code corresponding to the function definition. 
If the function is not found, the original source code is returned unchanged.

Args:
    source_code (str): The source code from which to remove the function.
    function_name (str): The name of the function to remove.

Returns:
    str: The modified source code with the function removed, or the original source code if the function is not found.
"""
You should write code starting with:
import ast

def remove_function(source_code: str, function_name: str) -> str:
    # TODO: Implement this function
    pass

