test(linux): drop imported open times and fix two test races

[datlechin]

Why

linux CI has been red since #3467. Fast checks, Flatpak and every package job fail a_version_1_connection_list_imports_as_it_was_written. #3467 made an import drop a file's last-opened times, and #3464's fixture test still expected them. Since #3473, two app tests also time out on some jobs.

Change

• The v1 import test expects no last-opened times. The fixture is unchanged.
• an_unreadable_history_says_why_where_it_is_opened waits for win.show-history to turn on. The action follows the window's own history, which can still be opening, and activating a disabled action does nothing.
• a_sorted_table_pages_by_offset serves a count of 1,000, like its sibling paging tests. With the old count of 2, a count landing after Next moved the pager back to the first page. That made a fourth read, and the wait for exactly three missed it.

Verified

stored_formats fails on linux and passes here. fmt, clippy and the tablepro lib suite pass in the Linux dev image, except sorting_10k_text_rows_finishes_within_one_second, which missed its 1 s bound at load average 56 and passes alone. Neither timeout reproduced locally; both races come from reading the code.