feat: Multiplexed sessions - Remove unnecessary divider comments

Signed-off-by: Taylor Curran <taylor.curran@improving.com>

Author: currantw

google/cloud/spanner_v1/session.py

@@ -537,18 +537,12 @@ def run_in_transaction(self, func, *args, **kw):
             previous_transaction_id: Optional[bytes] = None
 
             while True:
-                # [A] Build transaction
-                # ---------------------
-
                 txn = self.transaction()
                 txn.transaction_tag = transaction_tag
                 txn.exclude_txn_from_change_streams = exclude_txn_from_change_streams
                 txn.isolation_level = isolation_level
                 txn._previous_transaction_id = previous_transaction_id
 
-                # [B] Run user operation
-                # ----------------------
-
                 attempts += 1
                 span_attributes = dict(attempt=attempts)
 
@@ -593,9 +587,6 @@ def run_in_transaction(self, func, *args, **kw):
                     txn.rollback()
                     raise
 
-                # [C] Commit transaction
-                # ----------------------
-
                 try:
                     txn.commit(
                         return_commit_stats=log_commit_stats,