chore: Update upstream OpenTelemetry agent version and related deps (elastic#345)

Made with ❤️️ by updatecli

Author: obltmachine

gradle/libs.versions.toml

@@ -10,7 +10,7 @@ opentelemetryProto = "1.3.2-alpha"
 
 # otel agent, we rely on the '*-alpha' and get the non-alpha dependencies transitively
 # updated from upstream agent with .ci/update-upstream.sh
-opentelemetryJavaagentAlpha = "2.4.0-alpha"
+opentelemetryJavaagentAlpha = "2.6.0-alpha"
 
 # otel contrib
 # updated from upstream agent with .ci/update-upstream.sh