CI: Fix 502 Server Error: Bad Gateway errors for error path test case

For evaluating an error path of the code base, when connecting to
non-CrateDB servers, a connection to httpbin.org was made. Apparently,
they brought rate limiting in place, so the job would occasionally fail
when running on a larger test matrix.

Author: amotl

docs/by-example/http.rst

@@ -211,11 +211,11 @@ an exception is raised when the timeout is reached::
 
 When connecting to non-CrateDB servers, the HttpClient will raise a ConnectionError like this::
 
-    >>> http_client = HttpClient(["https://httpbin.org/html"])
+    >>> http_client = HttpClient(["https://example.org/"])
     >>> http_client.server_infos(http_client._get_server())
     Traceback (most recent call last):
     ...
-    crate.client.exceptions.ProgrammingError: Invalid server response of content-type 'text/html; charset=utf-8':
+    crate.client.exceptions.ProgrammingError: Invalid server response of content-type 'text/html; charset=UTF-8':
     ...
     >>> http_client.close()