esp_flash: decrease performance threshold of ESP32-S2

The data is based on 95% of minimal performance value from CI failure in the past 30 days.

components/idf_test/include/esp32s2/idf_performance_target.h

@@ -26,5 +26,5 @@
 #endif
 
 #ifndef IDF_PERFORMANCE_MIN_FLASH_SPEED_BYTE_PER_SEC_EXT_ERASE
-#define IDF_PERFORMANCE_MIN_FLASH_SPEED_BYTE_PER_SEC_EXT_ERASE                  52200
+#define IDF_PERFORMANCE_MIN_FLASH_SPEED_BYTE_PER_SEC_EXT_ERASE                  40300
 #endif