terminal: Fix alt-f and alt-b behavior (#23741)

Fixes alt+f and alt+b (word forward and word backward) behavior in
terminal

Release Notes:

- N/A

assets/keymaps/default-macos.json

@@ -834,6 +834,8 @@
       // Terminal.app compatibility
       "alt-left": ["terminal::SendText", "\u001bb"],
       "alt-right": ["terminal::SendText", "\u001bf"],
+      "alt-b": ["terminal::SendText", "\u001bb"],
+      "alt-f": ["terminal::SendText", "\u001bf"],
       // There are conflicting bindings for these keys in the global context.
       // these bindings override them, remove at your own risk:
       "up": ["terminal::SendKeystroke", "up"],