Remove out of date Prometheus Include Filter docs (#1725)
Remove out of date Prometheus Include Filter docs (#1725)

**Link to tracking Issue:** N/A, [PR 416](https://github.com/open-telemetry/opentelemetry-collector/pull/416) removed code that this documentation is describing.

**Documentation:** Removal of incorrect documentation.
open-telemetry/opentelemetry-collector-contrib,open-telemetry/opentelemetry-collector,open-telemetry/opentelemetry-collector,open-telemetry/opentelemetry-collector-contrib,open-telemetry/opentelemetry-collector