Convert Encoder callbacks to be boolean functions (#12805)

Co-authored-by: James Young <18669334+noroadsleft@users.noreply.github.com>

keyboards/clueboard/2x1800/2019/2019.h

@@ -29,8 +29,7 @@ enum TWOx1800_keycodes {
 #define SAFE_RANGE NEW_SAFE_RANGE
 
 // Encoder update function that returns true/false
-__attribute__ ((weak))
-bool encoder_update_keymap(int8_t index, bool clockwise);
+bool encoder_update_keymap(uint8_t index, bool clockwise);
 
 // Encoder button combo check
 void check_encoder_buttons(void);