chore: Add trailing lines to fix build warnings (#2743)

When building a unibody or central warnings get thrown for the backslash newlines at EOF in combos.h and input_listeners.h. Adding a trailing newline to the affected files rectifies this

Author: ReFil

app/include/zmk/combos.h

@@ -13,4 +13,4 @@
 #define ZMK_COMBOS_LEN                                                                             \
     COND_CODE_1(DT_HAS_COMPAT_STATUS_OKAY(zmk_combos),                                             \
                 (0 DT_FOREACH_CHILD_STATUS_OKAY(DT_INST(0, zmk_combos), ZMK_COMBOS_UTIL_ONE)),     \
-                (0))
+                (0))

app/include/zmk/input_listeners.h

@@ -11,4 +11,4 @@
 #define ZMK_INPUT_LISTENERS_UTIL_ONE(n) 1 +
 
 #define ZMK_INPUT_LISTENERS_LEN                                                                    \
-    (DT_FOREACH_STATUS_OKAY(zmk_input_listener, ZMK_INPUT_LISTENERS_UTIL_ONE) 0)
+    (DT_FOREACH_STATUS_OKAY(zmk_input_listener, ZMK_INPUT_LISTENERS_UTIL_ONE) 0)