Fix pylint C0103: rename single-char variable in setUp

Author: Krishnachaitanyakc

exporter/opentelemetry-exporter-otlp-proto-http/tests/test_proto_log_exporter.py

@@ -83,9 +83,9 @@ class TestOTLPHTTPLogExporter(unittest.TestCase):  # pylint: disable=too-many-pu
     def setUp(self):
         # Reset the DuplicateFilter between tests so that log suppression
         # from one test does not bleed into the next.
-        for f in _logger.filters:
-            if hasattr(f, "last_log"):
-                f.last_log = None
+        for log_filter in _logger.filters:
+            if hasattr(log_filter, "last_log"):
+                log_filter.last_log = None
 
     def test_constructor_default(self):
         exporter = OTLPLogExporter()