feat: remove Private restriction on write/tail

[jdowning]

New Private & Shield Kafka addons can use kafka:topics:write and kafka:topics:tail. This PR removes that guard.

[coveralls]

Coverage decreased (-0.1%) to 89.655% when pulling 14cc73c on private_can_write_tail into 0f6a36f on main.

[subakva]

I assume these commands will still fail if the customer hasn't adding their IP to the mtls list. Should we print a short message alerting them to that?

[jdowning]

@subakva if we cannot establish a connection, produce an error indicating failure to connect:

ᐅ heroku kafka:topics:write test1 "foo" KAFKA_URL -a myapp
 ▸    Could not connect to kafka

[subakva]

@subakva if we cannot establish a connection, produce an error indicating failure to connect:

ᐅ heroku kafka:topics:write test1 "foo" KAFKA_URL -a myapp
 ▸    Could not connect to kafka

I was thinking that if it's a private service addon, write an info log: "Writing to a private kafka requires adding your IP using data:mtls:ip-rules:create. I didn't intend this to be a blocker though. :)