Replace buffer lock magic numbers with defines (#5217)

* replace magic numbers with defines

wled00/util.cpp

@@ -561,7 +561,7 @@ void enumerateLedmaps() {
       ledMaps |= 1 << i;
 
       #ifndef ESP8266
-      if (requestJSONBufferLock(21)) {
+      if (requestJSONBufferLock(JSON_LOCK_LEDMAP_ENUM)) {
         if (readObjectFromFile(fileName, nullptr, pDoc, &filter)) {
           size_t len = 0;
           JsonObject root = pDoc->as<JsonObject>();