Update FirebaseCloudMessaging.cpp

[michaelchien1972]

fix for https: instead of http:

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[michaelchien1972]

I signed it!

[michaelchien1972]

In addition, some code changes may need to be done in ESP8266 Arduino bsp side.

File ESP8266HTTPClient.cpp

1. get ride of WiFiClientSecure function to by pass the validation on SHA1 signature of Firebase server

`
class TLSTraits : public TransportTraits
{
public:
TLSTraits(const String& fingerprint) :
_fingerprint(fingerprint)
{
}

std::unique_ptr<WiFiClient> create() override
{
    //return std::unique_ptr<WiFiClient>(new WiFiClientSecure());
    return std::unique_ptr<WiFiClient>(new WiFiClient());
}

bool verify(WiFiClient& client, const char* host) override
{
    //auto wcs = reinterpret_cast<WiFiClientSecure&>(client);
    //return wcs.verify(_fingerprint.c_str(), host);
   return true;
}

protected:
String _fingerprint;
};
`

2. force http to https

`
bool HTTPClient::begin(String url)
{
_transportTraits.reset(nullptr);

//_port = 80;
//if (!beginInternal(url, "http")) {
   //return false;
//}
_port = 443;
if (!beginInternal(url, "https")) {
    return false;
}
_transportTraits = TransportTraitsPtr(new TransportTraits());
return true;

}
`

[googlebot]

CLAs look good, thanks!

[proppy]

cc'ing @ed7coyne

[proppy]

Also see #347