vim: fix t not being repeatable with , (#7007)

This fixes `t` not being repeatable with `,` and `;` in normal mode.

Release Notes:

- Fixed `t` in Vim mode not being repeatable with `,` or `;`.

---------

Co-authored-by: Conrad <conrad@zed.dev>

assets/keymaps/vim.json

@@ -330,12 +330,7 @@
       "*": "vim::MoveToNext",
       "#": "vim::MoveToPrev",
       ";": "vim::RepeatFind",
-      ",": [
-        "vim::RepeatFind",
-        {
-          "backwards": true
-        }
-      ],
+      ",": "vim::RepeatFindReversed",
       "r": ["vim::PushOperator", "Replace"],
       "s": "vim::Substitute",
       "shift-s": "vim::SubstituteLine",