Remove legacy keycodes, part 4 (#18683)

* `KC_PGDOWN` -> `KC_PGDN`

* `KC_PSCREEN` -> `KC_PSCR`

* `KC_SCOLON` -> `KC_SCLN`

* `KC_BSLASH` -> `KC_BSLS`

* `KC_BSPACE` -> `KC_BSPC`

keyboards/handwired/d48/keymaps/default/keymap.c

@@ -143,7 +143,7 @@ bool process_record_user(uint16_t keycode, keyrecord_t *record) {
                         (new_time[4]) * 10 + (new_time[5])
                 );
                 for (int i = 0; i < 6; i++) {
-                    tap_code(KC_BSPACE);
+                    tap_code(KC_BACKSPACE);
                 }
             }
         }