Followup to #12293

Marlin/src/feature/mixing.h

@@ -43,13 +43,13 @@
 #ifdef RETRACT_SYNC_MIXING
   #define NR_MIXING_VIRTUAL_TOOLS (MIXING_VIRTUAL_TOOLS + 1)
   #define MIXER_AUTORETRACT_TOOL MIXING_VIRTUAL_TOOLS
-  #if NR_MIXING_VIRTUAL_TOOLS > 255
-    #error("MIXING_VIRTUAL_TOOLS must be <= 254!");
+  #if NR_MIXING_VIRTUAL_TOOLS > 254
+    #error "MIXING_VIRTUAL_TOOLS must be <= 254!"
   #endif
 #else
   #define NR_MIXING_VIRTUAL_TOOLS (MIXING_VIRTUAL_TOOLS)
   #if NR_MIXING_VIRTUAL_TOOLS > 255
-    #error("MIXING_VIRTUAL_TOOLS must be <= 255!");
+    #error "MIXING_VIRTUAL_TOOLS must be <= 255!"
   #endif
 #endif