UNO_91H: remove sectors, bootloader was disabled

This should be reverted once bootloader is supported.

Author: 0xc0170

targets/targets.json

@@ -9462,11 +9462,6 @@
         "inherits": ["RDA5981X"],
         "detect_code": ["8001"],
         "components_add": ["FLASHIAP"],
-        "mbed_ram_start": "0x00100080",
-        "mbed_ram_size": "0x1ff80",
-        "mbed_rom_start": "0x18001000",
-        "mbed_rom_size": "0x1F4000",
-        "sectors": [[0,4096]],
         "overrides": {
             "network-default-interface-type" : "WIFI"
         },