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`

users/dennytom/chording_engine/engine.part.1

@@ -91,10 +91,10 @@ bool handle_US_ANSI_shifted_keys(int16_t keycode, bool in) {
             regular_keycode = KC_RIGHT_BRACKET;
             break;
         case KC_PIPE:
-            regular_keycode = KC_BSLASH;
+            regular_keycode = KC_BACKSLASH;
             break;
         case KC_COLON:
-            regular_keycode = KC_SCOLON;
+            regular_keycode = KC_SEMICOLON;
             break;
         case KC_DOUBLE_QUOTE:
             regular_keycode = KC_QUOTE;