Fixes inconsistency in Sanctum::currentApplicationUrlWithPort() and Sanctum::currentRequestHost()

[denjaland]

When submitting #564, I didn't include a test using the actual config file.
Pulling in the new version to day, I noticed there was an issue with using it in the config as follows:

'stateful' => explode(',', env('SANCTUM_STATEFUL_DOMAINS', sprintf(
    '%s%s%s',
    'localhost,localhost:3000,127.0.0.1,127.0.0.1:8000,::1',
    Sanctum::currentApplicationUrlWithPort(),
    Sanctum::currentRequestHost()
))),

The problem is, that Sanctum::currentApplicationUrlWithPort() prepends the url with a comma, so it can be used here in the config.

personally, I don't like the prepend for the sake of making it usable in the explode(sprintf()) here, and would remove it, but that would be a breaking change, so I changed the implementation of the Sanctum::currentRequestHost() to be in line with how Sanctum::currentApplicationUrlWithPort() works, so this can be used in the same way.

My apologies for the oversight.