`-Wsign-compare` compiler warnings

[zfields]

Running this Arduino CLI command from the folder of a sketch that #includes the "ArduinoIoTCloud" library:

arduino-cli compile --verbose --warnings=all --build-property "build.extra_flags=-Wno-unused-variable -Wno-implicit-fallthrough -Wno-psabi -Wno-deprecated-copy -Wno-missing-field-initializers -Wno-vla -Wno-delete-non-virtual-dtor -Og -g" --fqbn arduino:mbed_opta:opta

results in this compiler warning:

~/Development/Arduino/libraries/ArduinoIoTCloud/src/ota/interface/OTAInterfaceDefault.cpp: In member function 'void OTADefaultCloudProcessInterface::parseOta(uint8_t*, size_t)':
~/Development/Arduino/libraries/ArduinoIoTCloud/src/ota/interface/OTAInterfaceDefault.cpp:205:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
       if(context->downloadedSize == http_client->contentLength()) {
          ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~/Development/Arduino/libraries/ArduinoIoTCloud/src/ota/interface/OTAInterfaceDefault.cpp:209:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
       if(context->downloadedSize > http_client->contentLength()) {
          ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~