Update cookbook.rst references to sqlalchemy#753

A fix for sqlalchemy#753 was merged in November 2020 and released in 1.5.0 in January 2021.
This updates the references to sqlalchemy#753 in cookbook.rst to note that a fix for sqlalchemy#753 has been released.

docs/build/cookbook.rst

@@ -1315,15 +1315,15 @@ follows::
                 elem.table_name, schema=elem.schema
             ) as batch_ops:
                 for table_elem in elem.ops:
-                    # work around Alembic issue #753
+                    # work around Alembic issue #753 (fixed in 1.5.0)
                     if hasattr(table_elem, "column"):
                         table_elem.column = table_elem.column.copy()
                     batch_ops.invoke(table_elem)
 
         elif hasattr(elem, "ops"):
             stack.extend(elem.ops)
         else:
-            # work around Alembic issue #753
+            # work around Alembic issue #753 (fixed in 1.5.0)
             if hasattr(elem, "column"):
                 elem.column = elem.column.copy()
             operations.invoke(elem)
@@ -1396,15 +1396,15 @@ at :func:`.autogenerate.compare_metadata`::
                 elem.table_name, schema=elem.schema
             ) as batch_ops:
                 for table_elem in elem.ops:
-                    # work around Alembic issue #753
+                    # work around Alembic issue #753 (fixed in 1.5.0)
                     if hasattr(table_elem, "column"):
                         table_elem.column = table_elem.column.copy()
                     batch_ops.invoke(table_elem)
 
         elif hasattr(elem, "ops"):
             stack.extend(elem.ops)
         else:
-            # work around Alembic issue #753
+            # work around Alembic issue #753 (fixed in 1.5.0)
             if hasattr(elem, "column"):
                 elem.column = elem.column.copy()
             operations.invoke(elem)