pgsql: vacuumlazy.c: prefer the term "cleanup lock".

vacuumlazy.c: prefer the term "cleanup lock".

The term "super-exclusive lock" is an acceptable synonym of "cleanup
lock". Even still, switching from one term to the other in the same
file is confusing. Standardize on "cleanup lock" within vacuumlazy.c.

Per a complaint from Andres Freund.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/276db875d4f9be2911582f367596d444d6986c77

Modified Files
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src/backend/access/heap/vacuumlazy.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)