pgsql: Turn "check" into assertion

Turn "check" into assertion

In commit 1813f951cad5, I mistakenly assumed that one particular
function named CheckSomething() checks Something. It doesn't, it merely
return the state to check. Fix by adding the necessary Assert() call.

Good chance to add trailers for commit 1813f951cad5:
Reviewed-by: Manuel Reyes Bravo <manuelreyesbravo(at)gmail(dot)com>
Reviewed-by: Antonin Houska <ah(at)cybertec(dot)at>
Reviewed-by: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>

Backpatch-through: 19
Discussion: https://postgr.es/m/CAA-aLv5MF6BLL+BWvix2Yw+CBardtH43AofPReQunhDZPNBtuA@mail.gmail.com

Branch
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REL_19_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/2b1d52b19799b9b34c0b5d5e2c465a259791a645

Modified Files
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src/backend/commands/repack.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)