pgsql: Remove redundant AssertVariableIsOfType uses

Remove redundant AssertVariableIsOfType uses

The uses of AssertVariableIsOfType in pg_upgrade are unnecessary
because the calls to upgrade_task_add_step() already check the
compatibility of the callback functions.

These were apparently copied from a previous coding style, but similar
removals were already done in commit 30b789eafe.

Reviewed-by: Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com>
Reviewed-by: Nathan Bossart <nathandbossart(at)gmail(dot)com>
Discussion: https://www.postgresql.org/message-id/flat/3d289481-7f76-409f-81c7-81824219cc75%40eisentraut.org

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/f3c96c9dff0c727afd1ef2ea976592c77cc809b5

Modified Files
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src/bin/pg_upgrade/check.c | 23 -----------------------
src/bin/pg_upgrade/function.c | 2 --
src/bin/pg_upgrade/info.c | 5 -----
src/bin/pg_upgrade/version.c | 2 --
4 files changed, 32 deletions(-)