Replace tests of ALTER DATABASE RESET TABLESPACE.

This unblocks rejection of that syntax.  One copy was a misspelling of
"SET TABLESPACE pg_default" that instead made no persistent changes.
The other copy just needed to populate a DATABASEOID syscache entry.
This slightly raises database.sql test coverage of catcache.c, while
dbcommands.c coverage remains the same.

Reported-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/1802710.1757608564@sss.pgh.pa.us

src/test/regress/expected/database.out

@@ -2,7 +2,7 @@ CREATE DATABASE regression_tbd
 	ENCODING utf8 LC_COLLATE "C" LC_CTYPE "C" TEMPLATE template0;
 ALTER DATABASE regression_tbd RENAME TO regression_utf8;
 ALTER DATABASE regression_utf8 SET TABLESPACE regress_tblspace;
-ALTER DATABASE regression_utf8 RESET TABLESPACE;
+ALTER DATABASE regression_utf8 SET TABLESPACE pg_default;
 ALTER DATABASE regression_utf8 CONNECTION_LIMIT 123;
 -- Test PgDatabaseToastTable.  Doing this with GRANT would be slow.
 BEGIN;
@@ -10,7 +10,7 @@ UPDATE pg_database
 SET datacl = array_fill(makeaclitem(10, 10, 'USAGE', false), ARRAY[5e5::int])
 WHERE datname = 'regression_utf8';
 -- load catcache entry, if nothing else does
-ALTER DATABASE regression_utf8 RESET TABLESPACE;
+ALTER DATABASE regression_utf8 RENAME TO regression_rename_rolled_back;
 ROLLBACK;
 CREATE ROLE regress_datdba_before;
 CREATE ROLE regress_datdba_after;

src/test/regress/sql/database.sql

@@ -2,7 +2,7 @@ CREATE DATABASE regression_tbd
 	ENCODING utf8 LC_COLLATE "C" LC_CTYPE "C" TEMPLATE template0;
 ALTER DATABASE regression_tbd RENAME TO regression_utf8;
 ALTER DATABASE regression_utf8 SET TABLESPACE regress_tblspace;
-ALTER DATABASE regression_utf8 RESET TABLESPACE;
+ALTER DATABASE regression_utf8 SET TABLESPACE pg_default;
 ALTER DATABASE regression_utf8 CONNECTION_LIMIT 123;
 
 -- Test PgDatabaseToastTable.  Doing this with GRANT would be slow.
@@ -11,7 +11,7 @@ UPDATE pg_database
 SET datacl = array_fill(makeaclitem(10, 10, 'USAGE', false), ARRAY[5e5::int])
 WHERE datname = 'regression_utf8';
 -- load catcache entry, if nothing else does
-ALTER DATABASE regression_utf8 RESET TABLESPACE;
+ALTER DATABASE regression_utf8 RENAME TO regression_rename_rolled_back;
 ROLLBACK;
 
 CREATE ROLE regress_datdba_before;