incorporate suggestions

Author: rahul2393

google/cloud/spanner_v1/_helpers.py

@@ -624,7 +624,6 @@ def _retry(
             if is_allowed and retries < retry_count:
                 if (
                     allowed_exceptions is not None
-                    and exc.__class__ in allowed_exceptions
                     and allowed_exceptions[exc.__class__] is not None
                 ):
                     allowed_exceptions[exc.__class__](exc)

google/cloud/spanner_v1/request_id_header.py

@@ -52,13 +52,10 @@ def with_request_id(
 def with_request_id_metadata_only(
     client_id, channel_id, nth_request, attempt, other_metadata=[], span=None
 ):
-    req_id = build_request_id(client_id, channel_id, nth_request, attempt)
-    all_metadata = (other_metadata or []).copy()
-    all_metadata.append((REQ_ID_HEADER_KEY, req_id))
-
-    if span:
-        span.set_attribute(X_GOOG_SPANNER_REQUEST_ID_SPAN_ATTR, req_id)
-
+    """Return metadata with request ID header, discarding the request ID value."""
+    all_metadata, _ = with_request_id(
+        client_id, channel_id, nth_request, attempt, other_metadata, span
+    )
     return all_metadata