Clean up header for uniform appearance throughout tests.

src/test/regress/input/misc.source

src/test/regress/sql/alter_table.sql

src/test/regress/sql/btree_index.sql

src/test/regress/sql/case.sql

src/test/regress/sql/errors.sql

src/test/regress/sql/hash_index.sql

src/test/regress/sql/join.sql

src/test/regress/sql/limit.sql

src/test/regress/sql/plpgsql.sql

src/test/regress/sql/portals.sql

src/test/regress/sql/portals_p2.sql

src/test/regress/sql/random.sql

src/test/regress/sql/rules.sql

src/test/regress/sql/select.sql

src/test/regress/sql/select_distinct.sql

src/test/regress/sql/select_distinct_on.sql

src/test/regress/sql/select_having.sql

src/test/regress/sql/select_implicit.sql

src/test/regress/sql/select_into.sql

src/test/regress/sql/select_views.sql