Revert "core: TokenAuth request_token fix missing auth" b/c oras-project#153

this was taken care in oras-project#153

This reverts commit 10e010b.

Signed-off-by: tarilabs <matteo.mortari@gmail.com>

Author: tarilabs

oras/auth/token.py

@@ -99,8 +99,6 @@ def request_token(self, h: auth_utils.authHeader) -> bool:
         """
         params = {}
         headers = {}
-        if self._basic_auth: # we exchange the basic auth for the token
-            headers["Authorization"] = "Basic %s" % self._basic_auth
 
         # Prepare request to retry
         if h.service: