Remove invalid return type annotation from http_request method

The annotation was invalid, resulting in mypy error:

error: "dict" expects 2 type arguments, but 1 given  [type-arg]

The `headers` field of the dictionary returned by this function is a `http.client.HTTPMessage` class object, while the
other field values are strings. I didn't find a way to specify this in a return type annotation and the current approach
is to provide annotations on a "best effort" basis (vs making them universally mandatory) so I settled on removing the
annotation entirely.

Author: per1234

reportsizedeltas/reportsizedeltas.py

@@ -581,7 +581,7 @@ def get_json_response(self, url: str):
         except Exception as exception:
             raise exception
 
-    def http_request(self, url: str, data: str | None = None) -> dict[str]:
+    def http_request(self, url: str, data: str | None = None):
         """Make a request and return a dictionary:
         read -- the response
         info -- headers