[release] Prepare release coreunstable-1.15.2-beta.1 (#7050)

Co-authored-by: opentelemetrybot <107717825+opentelemetrybot@users.noreply.github.com>

Author: otelbot-dotnet[bot]

src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md

@@ -7,6 +7,10 @@ Notes](../../RELEASENOTES.md).
 
 ## Unreleased
 
+## 1.15.2-beta.1
+
+Released 2026-Apr-08
+
 * Updated OpenTelemetry core component version(s) to `1.15.2`.
   ([#7049](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7049))
 

src/OpenTelemetry.Exporter.Prometheus.HttpListener/CHANGELOG.md

@@ -7,6 +7,10 @@ Notes](../../RELEASENOTES.md).
 
 ## Unreleased
 
+## 1.15.2-beta.1
+
+Released 2026-Apr-08
+
 * Updated OpenTelemetry core component version(s) to `1.15.2`.
   ([#7049](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7049))
 

src/OpenTelemetry.Shims.OpenTracing/CHANGELOG.md

@@ -6,6 +6,10 @@ Notes](../../RELEASENOTES.md).
 
 ## Unreleased
 
+## 1.15.2-beta.1
+
+Released 2026-Apr-08
+
 * Updated OpenTelemetry core component version(s) to `1.15.2`.
   ([#7049](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7049))