Remove MTB_MTS_DRAGONFLY target

Author: Marcelo Salazar

components/storage/blockdevice/COMPONENT_SD/mbed_lib.json

@@ -125,12 +125,6 @@
              "SPI_CLK":  "PTE2",
              "SPI_CS":   "PTE4"
         },
-        "MTB_MTS_DRAGONFLY": {
-             "SPI_MOSI": "SPI2_MOSI",
-             "SPI_MISO": "SPI2_MISO",
-             "SPI_CLK":  "SPI2_SCK",
-             "SPI_CS":   "SPI_CS2"
-        },
         "TB_SENSE_12": {
              "SPI_MOSI": "PC6",
              "SPI_MISO": "PC7",