Fix bad sanitycheck (#12748)

Marlin/src/inc/SanityCheck.h

 
 #endif
 
-#if HAS_MESH && DISABLED(JUNCTION_DEVIATION)
-  static_assert(DEFAULT_ZJERK > 0.1, "Low DEFAULT_ZJERK values are incompatible with mesh-based leveling.");
+#if HAS_MESH
+  #if DISABLED(JUNCTION_DEVIATION)
+    static_assert(DEFAULT_ZJERK > 0.1, "Low DEFAULT_ZJERK values are incompatible with mesh-based leveling.");
+  #endif
 #elif ENABLED(G26_MESH_VALIDATION)
   #error "G26_MESH_VALIDATION requires MESH_BED_LEVELING, AUTO_BED_LEVELING_BILINEAR, or AUTO_BED_LEVELING_UBL."
 #endif