Update regress tests to reflect removal of 'current'.

src/test/regress/expected/abstime-solaris-1947.out

src/test/regress/expected/abstime.out

src/test/regress/expected/horology-no-DST-before-1970.out

src/test/regress/expected/horology-solaris-1947.out

src/test/regress/expected/horology.out

src/test/regress/expected/timestamp.out

src/test/regress/expected/timestamptz.out

src/test/regress/sql/abstime.sql

src/test/regress/sql/horology.sql