Add a note on APM agent conflicts (elastic#2059)

Added a warning to the EDOT SDK troubleshooting docs to caution users
that EDOT SDKs should not be used in the same application process as
other APM agents.

Resolves part of [this
issue](elastic#2025).

Author: alexandra5000

troubleshoot/ingest/opentelemetry/edot-sdks/index.md

@@ -20,3 +20,7 @@ Find solutions to common issues with EDOT SDKs.
 - [Node.js](/troubleshoot/ingest/opentelemetry/edot-sdks/nodejs/index.md)
 - [PHP](/troubleshoot/ingest/opentelemetry/edot-sdks/php/index.md)
 - [Python](/troubleshoot/ingest/opentelemetry/edot-sdks/python/index.md)
+
+:::{warning}
+Avoid using EDOT SDKs alongside any other APM agent, including Elastic APM agents. Running multiple agents in the same application process may lead to unexpected behavior, conflicting instrumentation, or duplicated telemetry.
+:::