test(a2a): drop no-op sys.path.insert from new regression tests

pytest's rootdir handling and the installed package already make
litellm importable; these were copy-paste no-ops that also made the
guardrail_translation test's imports depend on the working directory
it happens to run from.

Resolves the TQ003 test-quality budget breach flagged in the lint job.

tests/test_litellm/a2a_protocol/test_regression_issue_28577.py

@@ -1,11 +1,3 @@
-import sys
-import os
-
-# Add litellm to sys.path
-sys.path.insert(
-    0, os.path.abspath(os.path.join(os.path.dirname(__file__), "../../../"))
-)
-
 from litellm.llms.a2a.chat.transformation import A2AConfig
 from litellm.llms.a2a.common_utils import extract_text_from_a2a_message
 

tests/test_litellm/llms/a2a/chat/guardrail_translation/test_handler.py

@@ -9,14 +9,10 @@ inspected `kind: "text"` parts, so guarded output checks were skipped for
 that content path.
 """
 
-import os
-import sys
 from typing import Any, Literal, Optional
 
 import pytest
 
-sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "../../../../../..")))
-
 from litellm.integrations.custom_guardrail import CustomGuardrail
 from litellm.llms.a2a.chat.guardrail_translation.handler import A2AGuardrailHandler
 from litellm.types.utils import GenericGuardrailAPIInputs

tests/test_litellm/responses/test_regression_issue_28553.py

@@ -1,11 +1,3 @@
-import sys
-import os
-
-# Add litellm to sys.path
-sys.path.insert(
-    0, os.path.abspath(os.path.join(os.path.dirname(__file__), "../../../"))
-)
-
 from litellm.proxy.common_request_processing import ProxyBaseLLMRequestProcessing