Added a define to format the spiffs in SPIFFS_Test.ino (#1662)

* Added a define to format the spiffs in SPIFFS_Test.ino

* Uncommented the define

* Matched define names

libraries/SPIFFS/examples/SPIFFS_Test/SPIFFS_Test.ino

 #include "FS.h"
 #include "SPIFFS.h"
 
+/* You only need to format SPIFFS the first time you run a
+   test or else use the SPIFFS plugin to create a partition
+   https://github.com/me-no-dev/arduino-esp32fs-plugin */
+#define FORMAT_SPIFFS_IF_FAILED true
+
 void listDir(fs::FS &fs, const char * dirname, uint8_t levels){
     Serial.printf("Listing directory: %s\r\n", dirname);
 
@@ -151,7 +156,7 @@ void testFileIO(fs::FS &fs, const char * path){
 
 void setup(){
     Serial.begin(115200);
-    if(!SPIFFS.begin()){
+    if(!SPIFFS.begin(FORMAT_SPIFFS_IF_FAILED)){
         Serial.println("SPIFFS Mount Failed");
         return;
     }