Address PR review feedback: remove unused imports, simplify loop, add response_mode

Agent-Logs-Url: https://github.com/AzureAD/microsoft-authentication-library-for-python/sessions/20f5cbfd-04ca-45f5-8c71-f8df1d00a01e

Co-authored-by: ashok672 <83938949+ashok672@users.noreply.github.com>

Author: Copilot

tests/test_oidc.py

@@ -50,7 +50,8 @@ def test_oauth2_state_is_url_safe_and_unpredictable(self):
         states = set()
         for _ in range(10):
             flow = client.initiate_auth_code_flow(
-                redirect_uri="http://localhost", scope=["openid"])
+                redirect_uri="http://localhost", scope=["openid"],
+                response_mode="form_post")
             state = flow["state"]
             self.assertRegex(state, r'^[A-Za-z0-9_-]+$',
                 "state should be URL-safe")
@@ -67,7 +68,8 @@ def test_oidc_nonce_is_url_safe_and_unpredictable(self):
         nonces = set()
         for _ in range(10):
             flow = client.initiate_auth_code_flow(
-                redirect_uri="http://localhost", scope=["openid"])
+                redirect_uri="http://localhost", scope=["openid"],
+                response_mode="form_post")
             nonce = flow["nonce"]
             self.assertRegex(nonce, r'^[A-Za-z0-9_-]+$',
                 "nonce should be URL-safe")