Fix psql \if expression

The expression part of the psql \if cannot contain actual SQL expression
and is instead much more limited.

A valid value is any unambiguous case-insensitive match for one of: true, false, 1, 0, on, off, yes, no.

See https://www.postgresql.org/docs/current/app-psql.html

test/sql/updates/setup.continuous_aggs.v2.sql

@@ -21,8 +21,7 @@ SELECT
   :ts_major >= 2 AS has_create_mat_view,
   :ts_major >= 2 AS has_continuous_aggs_policy,
   :ts_major = 2 AND :ts_minor >= 7 AS has_continuous_aggs_finals_form,
-  :ts_major = 2 AND :ts_minor IN (7,8) AS has_continuous_aggs_finalized_option,
-  :ts_major = 2 AND :ts_minor IN (5) AS has_cagg_rename_col_bug
+  :ts_major = 2 AND :ts_minor IN (7,8) AS has_continuous_aggs_finalized_option
   FROM pg_extension
  WHERE extname = 'timescaledb' \gset
 
@@ -138,24 +137,13 @@ SELECT generate_series('2018-11-01 00:00'::timestamp, '2018-12-15 00:00'::timest
 
     -- ALTER VIEW cannot rename columns before PG13, but ALTER TABLE
     -- works for views.
-    --
-    -- Renaming one column that is used in the group by and one that is
-    -- not in the group by. Both should work.
     ALTER TABLE rename_cols RENAME COLUMN bucket TO "time";
-\if :has_cagg_rename_col_bug == false
-    ALTER TABLE rename_cols RENAME COLUMN humidity TO moisture;
-\endif
 \else
       GROUP BY bucket, location
       HAVING min(location) >= 'NYC' and avg(temperature) > 2 WITH NO DATA;
     SELECT add_continuous_aggregate_policy('mat_before', NULL, '-30 days'::interval, '336 h');
 
-    -- Renaming one column that is used in the group by and one that
-    -- is not in the group by. Both should work.
     ALTER MATERIALIZED VIEW rename_cols RENAME COLUMN bucket TO "time";
-\if :has_cagg_rename_col_bug == false
-    ALTER MATERIALIZED VIEW rename_cols RENAME COLUMN humidity TO moisture;
-\endif
 \endif
 
 \if :WITH_SUPERUSER