Remove ENABLE_A365_OBSERVABILITY_PER_REQUEST_EXPORT - not applicable for Python

Co-authored-by: nikhilNava <211831449+nikhilNava@users.noreply.github.com>

Author: Copilot

libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/constants.py

@@ -23,7 +23,6 @@
 ENABLE_OBSERVABILITY = "ENABLE_OBSERVABILITY"
 ENABLE_A365_OBSERVABILITY_EXPORTER = "ENABLE_A365_OBSERVABILITY_EXPORTER"
 ENABLE_A365_OBSERVABILITY = "ENABLE_A365_OBSERVABILITY"
-ENABLE_A365_OBSERVABILITY_PER_REQUEST_EXPORT = "ENABLE_A365_OBSERVABILITY_PER_REQUEST_EXPORT"
 
 # GenAI semantic conventions
 GEN_AI_CLIENT_OPERATION_DURATION_METRIC_NAME = "gen_ai.client.operation.duration"