PSRAM fix not needed for Denky D4 (platformio#775)

Author: Jason2866

boards/denky_d4.json

@@ -6,9 +6,7 @@
     "core": "esp32",
     "extra_flags": [
       "-DARDUINO_DENKY_PICOV3",
-      "-DBOARD_HAS_PSRAM",
-      "-mfix-esp32-psram-cache-issue",
-      "-mfix-esp32-psram-cache-strategy=memw"
+      "-DBOARD_HAS_PSRAM"
     ],
     "f_cpu": "240000000L",
     "f_flash": "80000000L",