Обсуждение: pgsql: Update comments about progress reporting by index_drop

Update comments about progress reporting by index_drop

Michaël Paquier complained that index_drop is requesting progress
reporting for non-obvious reasons, so let's add a comment to explain
why.

Discussion: https://postgr.es/m/20191017010412.GH2602@paquier.xyz

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/029390a0909f5be74e3dd9bc1ad4dbf1506287d7

Modified Files
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src/backend/catalog/index.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)