Unexcepted result in content-type

[MarcHagen]

resp.headers.get("content-type") can return application/json; charset=utf-8 which fails the check.

Please see esphome/issues#2183
This could fix: esphome/issues#2183 , esphome/issues#2193

The problem is here, ports is not a array but plain text.

dashboard/src/api/serial-ports.ts

Line 12 in ed3eed0

.then((ports) => ports.filter((port) => port.port !== "OTA"));

Then fetchApi doesn't appear to return a javascript array but regular text.
Which is wierd because this is checked here:

dashboard/src/api/index.ts

Lines 13 to 15 in ed3eed0

	return resp.headers.get("content-type") === "application/json"
	? resp.json()
	: resp.text();

This is not a browser cache problem.
/serial-ports does indeed return a json text, and the content-type: application/json; charset=utf-8 header.

And that's where it goes wrong.
In my testing, resp.headers.get("content-type") returned: application/json; charset=utf-8 which is not the same as application/json.
I'm not quite sure where the charset=utf-8 comes from, but this PR fixes the issue quite easly.

Another posibility is to force resp.json() wrapped in a try / catch.

try {
    return resp.json();
} catch(err) {
   return resp.text();
}

[balloob]

Thanks!