keymaps: Avoid capturing ctrl-r in the terminal (#53301)

Update macOS and Linux's default keymaps such that, in the `Terminal`
context, `ctrl-r` does send the `ctrl-r` keystrokes. This was no longer
the case with recent changes to enable `ctrl-r` to map to
`projects::OpenRecent` which prevented users to use history search in
shells like bash and zsh, for example.

Release Notes:

- N/A

assets/keymaps/default-linux.json

@@ -1189,6 +1189,7 @@
       "ctrl-e": ["terminal::SendKeystroke", "ctrl-e"],
       "ctrl-o": ["terminal::SendKeystroke", "ctrl-o"],
       "ctrl-w": ["terminal::SendKeystroke", "ctrl-w"],
+      "ctrl-r": ["terminal::SendKeystroke", "ctrl-r"],
       "ctrl-backspace": ["terminal::SendKeystroke", "ctrl-w"],
       "ctrl-shift-a": "editor::SelectAll",
       "find": "buffer_search::Deploy",

assets/keymaps/default-macos.json

@@ -1269,6 +1269,7 @@
       "escape": ["terminal::SendKeystroke", "escape"],
       "enter": ["terminal::SendKeystroke", "enter"],
       "ctrl-c": ["terminal::SendKeystroke", "ctrl-c"],
+      "ctrl-r": ["terminal::SendKeystroke", "ctrl-r"],
       "ctrl-backspace": ["terminal::SendKeystroke", "ctrl-w"],
       "shift-pageup": "terminal::ScrollPageUp",
       "cmd-up": "terminal::ScrollPageUp",