Revert "Allow units to be specified in relation option setting value."

This reverts commit e23014f3d4.

As the side effect of the reverted commit, when the unit is
specified, the reloption was stored in the catalog with the unit.
This broke pg_dump (specifically, it prevented pg_dump from
outputting restorable backup regarding the reloption) and
turned the buildfarm red. Revert the commit until the fixed
version is ready.

src/test/regress/expected/alter_table.out

@@ -1811,20 +1811,6 @@ Check constraints:
     "test_inh_check_a_check" CHECK (a::double precision > 10.2::double precision)
 Inherits: test_inh_check
 
--- Set a storage parameter with unit
-CREATE TABLE test_param_unit (a text) WITH (autovacuum_vacuum_cost_delay = '80ms');
-ALTER TABLE test_param_unit SET (autovacuum_vacuum_cost_delay = '3min');
-ERROR:  value 3min out of bounds for option "autovacuum_vacuum_cost_delay"
-DETAIL:  Valid values are between "0" and "100".
-ALTER TABLE test_param_unit SET (autovacuum_analyze_threshold = '3min'); -- fails
-ERROR:  invalid value for integer option "autovacuum_analyze_threshold": 3min
-\d+ test_param_unit
-                  Table "public.test_param_unit"
- Column | Type | Modifiers | Storage  | Stats target | Description 
---------+------+-----------+----------+--------------+-------------
- a      | text |           | extended |              | 
-Options: autovacuum_vacuum_cost_delay=80ms
-
 --
 -- lock levels
 --

src/test/regress/sql/alter_table.sql

@@ -1254,12 +1254,6 @@ ALTER TABLE test_inh_check ALTER COLUMN a TYPE numeric;
 \d test_inh_check
 \d test_inh_check_child
 
--- Set a storage parameter with unit
-CREATE TABLE test_param_unit (a text) WITH (autovacuum_vacuum_cost_delay = '80ms');
-ALTER TABLE test_param_unit SET (autovacuum_vacuum_cost_delay = '3min');
-ALTER TABLE test_param_unit SET (autovacuum_analyze_threshold = '3min'); -- fails
-\d+ test_param_unit
-
 --
 -- lock levels
 --