Use recommended form for "Authorization" header in GitHub API requests

The previous "token" format works fine, but the "Bearer" format is the one used in the snippets in the GitHub REST API
documentation so this format makes the code easier to understand.

Author: per1234

reportsizedeltas/reportsizedeltas.py

@@ -627,7 +627,7 @@ def raw_http_request(self, url: str, data: bytes | None = None):
 
         headers = {
             "Accept": "application/vnd.github+json",
-            "Authorization": "token " + self.token,
+            "Authorization": "Bearer " + self.token,
             # GitHub recommends using user name as User-Agent (https://developer.github.com/v3/#user-agent-required)
             "User-Agent": self.repository_name.split("/")[0],
         }

reportsizedeltas/tests/test_reportsizedeltas.py

@@ -891,7 +891,7 @@ def test_raw_http_request(mocker):
         url=url,
         headers={
             "Accept": "application/vnd.github+json",
-            "Authorization": "token " + token,
+            "Authorization": "Bearer " + token,
             "User-Agent": user_name,
         },
         data=data,