Update changelog && change variable in test

CHANGELOG.md

@@ -22,7 +22,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
-- `opentelemetry-instrumentation-flask` Add http route to metric attributes
+- `opentelemetry-instrumentation-flask` Add `http.route` to metric attributes
   ([#2506](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2506))
 - `opentelemetry-sdk-extension-aws` Register AWS resource detectors under the
   `opentelemetry_resource_detector` entry point

instrumentation/opentelemetry-instrumentation-flask/tests/test_programmatic.py

@@ -85,6 +85,9 @@ def expected_attributes_new(override_attributes):
     return default_attributes
 
 
+_server_duration_attrs_old_copy = _server_duration_attrs_old.copy()
+_server_duration_attrs_old_copy.append("http.route")
+
 _expected_metric_names_old = [
     "http.server.active_requests",
     "http.server.duration",
@@ -95,7 +98,7 @@ def expected_attributes_new(override_attributes):
 ]
 _recommended_metrics_attrs_old = {
     "http.server.active_requests": _server_active_requests_count_attrs_old,
-    "http.server.duration": _server_duration_attrs_old,
+    "http.server.duration": _server_duration_attrs_old_copy,
 }
 _recommended_metrics_attrs_new = {
     "http.server.active_requests": _server_active_requests_count_attrs_new,
@@ -109,7 +112,7 @@ def expected_attributes_new(override_attributes):
 )
 _recommended_metrics_attrs_both = {
     "http.server.active_requests": _server_active_requests_count_attrs_both,
-    "http.server.duration": _server_duration_attrs_old,
+    "http.server.duration": _server_duration_attrs_old_copy,
     "http.server.request.duration": _server_duration_attrs_new,
 }