doc correction

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/12/ddl-generated-columns.html
Description:

https://www.postgresql.org/docs/12/ddl-generated-columns.html

In the below
"Consider the differences between a column with a default and a generated
column. The column default is evaluated once when the row is first inserted
if no other value was provided; a generated column is updated whenever the
row changes and cannot be overridden. A column default may not refer to
other columns of the table; a generation expression would normally do so. A
column default can use volatile functions, for example random() or functions
referring to the current time; this is not allowed for generated columns."

"a generation expression would normally do so" should be changed to "a
generated column" for easier reading