Tweak query to fetch IVR calls to retry to match new index

[rowanseymour]

Goes with nyaruka/rapidpro#3486

[codecov]

Codecov Report

Merging #477 (2b27052) into main (88108ab) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #477   +/-   ##
=======================================
  Coverage   56.93%   56.93%           
=======================================
  Files         123      123           
  Lines        8606     8606           
=======================================
  Hits         4900     4900           
  Misses       2929     2929           
  Partials      777      777           

Impacted Files	Coverage Δ
core/models/channel_connection.go	24.32% <ø> (ø)

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