ports/*/boards/*/board.json: Remove "id" field.

This was used to override the firmware filename generated by the build
server (to match the historical name before board definitions existed).

Now we're making everything use the board definition name (i.e. the
directory name).

This work was funded through GitHub Sponsors.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

ports/esp8266/boards/GENERIC/board.json

@@ -7,7 +7,6 @@
         "External Flash",
         "WiFi"
     ],
-    "id": "esp8266",
     "images": [],
     "mcu": "esp8266",
     "product": "ESP8266 with 2MiB+ flash",

ports/esp8266/boards/GENERIC_1M/board.json

@@ -7,7 +7,6 @@
         "External Flash",
         "WiFi"
     ],
-    "id": "esp8266-1m",
     "images": [],
     "mcu": "esp8266",
     "product": "ESP8266 with 1MiB flash",

ports/esp8266/boards/GENERIC_512K/board.json

@@ -7,7 +7,6 @@
         "External Flash",
         "WiFi"
     ],
-    "id": "esp8266-512k",
     "images": [],
     "mcu": "esp8266",
     "product": "ESP8266 with 512kiB flash",