Update references to otlphttp in usage/examples/documentation

[codeboten]

Component(s)

exporter/otlp, exporter/otlp_http

Describe the issue you're reporting

A quick search through the OTel repos returns many different places where the otlphttp exporter is configured.

As a result #14397, the new name otlp_http should be used. I'll open issues in various other repos to reference this one.

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