Modify manifest to use another API to download files from github

Author: mverdy

bin/manifest.json

@@ -1,9 +1,9 @@
 {"lora_modem": {
   "version": "1.00.07",
-  "url": "https://raw.githubusercontent.com/Lora-net/radio_firmware_images/master/lr1110/modem/lr1110_modem_1.0.7.h",
+  "url": "https://api.github.com/repos/Lora-net/radio_firmware_images/contents/lr1110/modem/lr1110_modem_1.0.7.h",
   "hash": "e8244951e68f80b92a1f8f2bb852ca10"},
   "tkr_app": {
     "version": "1.01.01",
-    "url": "https://raw.githubusercontent.com/Lora-net/lora_edge_tracker_ref_design/master/bin/lr1110_modem_tracker_sdk.bin",
+    "url": "https://api.github.com/repos/Lora-net/lora_edge_tracker_ref_design/contents/bin/lr1110_modem_tracker_sdk.bin",
     "hash": "bf974547e39549044cee8ec92b6092ab"}
 }