[R] Test failure with dbplyr 2.6.0 - remote_con() path changed from x$src$con to x$con

[thisisnic]

dbplyr 2.6.0 (released 2026-06-17) changed remote_con() from returning x$src$con to x$con, after refactoring tbl_sql/tbl_lazy to store the connection directly as a top-level field (tidyverse/dbplyr#1680).

This breaks the test at r/tests/testthat/test-duckdb.R:131-137 which simulates a non-DuckDB connection by overriding class(ds_rt$src$con). Since remote_con() now reads from ds_rt$con, the override has no effect, to_arrow() sees a valid duckdb_connection, and the expected error is never thrown.

Failing on main CI (Windows R release) since 2026-06-18 and 8 nightly R test jobs.

Fix: update line 132 to also/instead override ds_rt$con.