Remove outdated comment about key binding being disabled (helix-edito…

…r#10717)

I just used the `=` binding to format a selection in a CSS file in helix 23.10 (5931a46) so removing this comment as outdated.

book/src/keymap.md

@@ -89,7 +89,7 @@ Normal mode is the default mode when you launch helix. You can return to it from
 | `"` `<reg>` | Select a register to yank to or paste from | `select_register` |
 | `>` | Indent selection | `indent` |
 | `<` | Unindent selection | `unindent` |
-| `=` | Format selection (currently nonfunctional/disabled) (**LSP**) | `format_selections` |
+| `=` | Format selection (**LSP**)  | `format_selections` |
 | `d` | Delete selection | `delete_selection` |
 | `Alt-d` | Delete selection, without yanking | `delete_selection_noyank` |
 | `c` | Change selection (delete and enter insert mode) | `change_selection` |