samples: update documentation

[ndr-brt]

What this PR changes/adds

Update sample-03 documentation

Why it does that

It was out of date.

Further notes

Linked Issue(s)

Closes #1218

Checklist

• added appropriate tests?
• performed checkstyle check locally?
• added/updated copyright headers?
• documented public classes/methods?
• added/updated relevant documentation?
• added relevant details to the changelog? (skip with label no-changelog)
• formatted title correctly? (take a look at the CONTRIBUTING and styleguide for details)

[ronjaquensel]

I think it would make sense to either add a few sentences about the token-based API authentication or remove it from the build file. Currently it's there, but is never mentioned in the README. Therefore, when someone runs this sample and tries to call the health endpoint again to see the new log prefix, they'll get a 403.

[ndr-brt]

@ronjaquensel yeah, you're right, removed it from the build file and from the readme

[florianrusch-zf]

@ronjaquensel yeah, you're right, removed it from the build file and from the readme

@ndr-brt The other samples that build on this one also use token based. Here you should possibly also take this out.

[ndr-brt]

@florianrusch-zf I don't know, in sample-04.0 the "auth key" stuff is explained in the README, maybe removing it will remove value from the sample?

[florianrusch-zf]

@ndr-brt Ahhhh sorry, of course! Then everything is fine for me so far. Thank you! :-)