Remove @Service from InjectExtension as not required

[rbygrave]

I think it is clearer if @service is not here as it isn't used or required.

[SentryMan]

No it's needed, avaje spi only know how to avoid colliding correctly if @Service is there.

[rbygrave]

avaje spi only know how to avoid colliding

It avoids collision via the hard coded exclusions, so in that way it isn't needed. I'm thinking you agree as you reopened this PR?

[SentryMan]

I closed it as a mistake before we could talk it out

[rbygrave]

Ok, we can close this. Copying description from jsonb here:

---

This is required in order to support the use of avaje-spi-serivce @ServiceProvider with
other custom InjectExtension service implementations.

Custom InjectExtension implementations can be registered explicitly with META-INF/services
entries OR we can use @ServiceProvider for that to automatically happen.

The reason the @Service is required on the InjectExtension interface is so that avaje-spi-service
actually ignores it correctly (and thus allowing avaje-jsonb-generator to process it with the
generated InjectExtension implementations). Without this  avaje-spi-service incorrectly
assumes that the top level interface is the service interface and then doesn't ignore it and instead
generates an incorrect file in target/classes/META-INF/services.