[instrumentation-system-metrics] Remove labels configuration

[codeboten]

As per Aaron's comment, the labels configuration parameter is no longer needed as views offer the same functionality.

It looks like this just adds extra attributes to all measurements. We should probably remove this?

We can do it in a separate PR though as this is just restoring the package

Originally posted by @aabmass in #1012 (comment)

[pridhi-arora]

@srikanthccv Can I take this up?

[srikanthccv]

Let me know if you need help understanding the issue if it's not already clear.