Fix an ALTER TABLE test case so that it actually tests what the comment says it

is testing.  Ah, the perils of making keywords optional ...

src/test/regress/expected/alter_table.out

@@ -351,7 +351,8 @@ alter table atacc3 inherit atacc2;
 ERROR:  child table is missing column "test2"
 -- fail due to mismatched data type
 alter table atacc3 add test2 bool;
-alter table atacc3 add inherit atacc2;
+alter table atacc3 inherit atacc2;
+ERROR:  child table "atacc3" has different type for column "test2"
 alter table atacc3 drop test2;
 -- succeed
 alter table atacc3 add test2 int;

src/test/regress/sql/alter_table.sql

@@ -373,7 +373,7 @@ alter table atacc3 rename test2 to testx;
 alter table atacc3 inherit atacc2;
 -- fail due to mismatched data type
 alter table atacc3 add test2 bool;
-alter table atacc3 add inherit atacc2;
+alter table atacc3 inherit atacc2;
 alter table atacc3 drop test2;
 -- succeed
 alter table atacc3 add test2 int;