docs(linux): update the roadmap for the merged release fixes

[datlechin]

Why

linux/ROADMAP.md still described the tree before #3463, #3468, #3470 and #3473 merged.

Change

• Criterion 4: pages seek by key or walk PostgreSQL heap blocks, with OFFSET only in three cases; the Docker paging tests are listed. Still needed: the 1,000,000-row test with time and memory bounds.
• Criterion 8: keyboard sort from the cell menu, named fields, focus hand-off and announcements hold. Still needed: resizing columns from the keyboard and the manual pass.
• Sidebar Refresh and the reread after DDL, Ctrl+O, Ctrl+S and Save As, the 100,000-row run limit, and crash reports go into the capability tables.
• The backlog drops the README install commands and the crash report, both done.
• Two em dashes in production-audit.md become colons.