pgsql: Make compression.sql regression test independent of default.

Make compression.sql regression test independent of default.

This test will fail in "make installcheck" if the installation's
default_toast_compression setting is not 'pglz'.  Make it robust
against that situation.

Dilip Kumar

Discussion: https://postgr.es/m/CAFiTN-t0w+Rc2U3S+y=7KWcLuOYNB5MfWeGdNa7+pg0UovVdcQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/fd1ac9a548966786cf7978e590be816c55936a50

Modified Files
--------------
src/test/regress/expected/compression.out   | 3 +++
src/test/regress/expected/compression_1.out | 3 +++
src/test/regress/sql/compression.sql        | 4 ++++
3 files changed, 10 insertions(+)