Replace address pointing toward malicious web page

FIX python#102627 

partial fix only: would require to go through the entire documentation

Author: Blind4Basics

Doc/library/concurrent.futures.rst

@@ -202,7 +202,7 @@ ThreadPoolExecutor Example
            'http://www.cnn.com/',
            'http://europe.wsj.com/',
            'http://www.bbc.co.uk/',
-           'http://some-made-up-domain.com/']
+           'http://example.com/non-existing-page']
 
    # Retrieve a single page and report the URL and contents
    def load_url(url, timeout):