[docs] Update readme to mention SAPM exporter instead of OTLP HTTP (#5718)

Author: dmitryax

README.md

@@ -49,12 +49,8 @@ provides a unified way to receive, process, and export metric, trace, and log
 data for [Splunk Observability Cloud](https://www.splunk.com/en_us/observability.html):
 
 - [Splunk APM](https://docs.splunk.com/Observability/apm/intro-to-apm.html#nav-Introduction-to-Splunk-APM) via the
-  [`sapm`
-  exporter](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/exporter/sapmexporter).
-  The [`otlphttp`
-  exporter](https://github.com/open-telemetry/opentelemetry-collector/tree/main/exporter/otlphttpexporter)
-  can be used with a [custom
-  configuration](https://github.com/signalfx/splunk-otel-collector/blob/main/cmd/otelcol/config/collector/otlp_config_linux.yaml).
+  [`otlphttp`
+  exporter](https://github.com/open-telemetry/opentelemetry-collector/tree/main/exporter/otlphttpexporter).
   More information available
   [here](https://docs.splunk.com/Observability/gdi/opentelemetry/opentelemetry.html#nav-Install-and-configure-Splunk-Distribution-of-OpenTelemetry-Collector).
 - [Splunk Infrastructure