Update release notes.

src/Microsoft.Graph.Core/Microsoft.Graph.Core.csproj

@@ -21,25 +21,9 @@
     <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
     <VersionPrefix>1.15.0</VersionPrefix>
     <VersionSuffix></VersionSuffix>
-    <PackageReleaseNotes>April 2019 Release Summary (version 1.15.0)
-
-New Features:
-Added Graph client factory to create HTTP clients that are pre-configured to make requests to Graph APIs.
-Added batch request content that make is easy to create payloads for a Graph batch request.
-Added batch response content to process batch responses from Graph.
-Added compression middleware handler to request, detect and decompress response bodies from Graph service.
-Added response handler to process native HTTP response messages to strongly typed Graph objects.
-Added page iterator to process items in a response page and provide control for iterating across response pages.
-
-Fixes:
-Fixed issue #136.
-Fixed issue #205.
-Fixed issue #401.
-Fixed issue #413.
-Fixed issue #431.
-Fixed issue #435.
-Fixed issue #447.
-Fixed issue #449.
+    <PackageReleaseNotes>
+      - Fix #481. Use native HTTP client handlers for Xamarin.iOS and Xamarin.Android.
+      - Fix #482. Skip CompressionHandler when NSUrlSessionHandler is used.
     </PackageReleaseNotes>
   </PropertyGroup>
   <!--We manually configure LanguageTargets for Xamarin due to .Net SDK TFMs limitation https://github.com/dotnet/sdk/issues/491 -->