Add notice about the OTeL collector (#891)
Add notice about the OTeL collector (#891)

Add notice about the OTeL collector, add changes from technical review, and update gateway/README.md

Co-authored-by: Brian Ashby <816441af6f752d29c3f5a9ea066e49a6fb82a76a@users.noreply.github.com>
Co-authored-by: Steve Flanders <22609c169b33f249677b1d5327f6cd3ec33cd532@splunk.com>
Co-authored-by: Brian Ashby <816441af6f752d29c3f5a9ea066e49a6fb82a76a@users.noreply.github.com>
signalfx/integrations,signalfx/integrations