Rely on SSE in shared framework

Author: captainsafia

eng/SharedFramework.External.props

@@ -42,7 +42,6 @@
     <ExternalAspNetCoreAppReference Include="Microsoft.Extensions.Options.DataAnnotations"                 Version="$(MicrosoftExtensionsOptionsDataAnnotationsVersion)" />
     <ExternalAspNetCoreAppReference Include="Microsoft.Extensions.Options"                                 Version="$(MicrosoftExtensionsOptionsVersion)" />
     <ExternalAspNetCoreAppReference Include="Microsoft.Extensions.Primitives"                              Version="$(MicrosoftExtensionsPrimitivesVersion)" />
-    <ExternalAspNetCoreAppReference Include="System.Net.ServerSentEvents"                                 Version="$(SystemNetServerSentEvents)" />
     <ExternalAspNetCoreAppReference Include="System.Security.Cryptography.Xml"                             Version="$(SystemSecurityCryptographyXmlVersion)" />
     <ExternalAspNetCoreAppReference Include="System.Threading.RateLimiting"                                Version="$(SystemThreadingRateLimitingVersion)" />
 

src/Framework/test/TestData.cs

@@ -155,7 +155,6 @@ static TestData()
                 "Microsoft.Net.Http.Headers",
                 "System.Diagnostics.EventLog",
                 "System.Diagnostics.EventLog.Messages",
-                "System.Net.ServerSentEvents",
                 "System.Security.Cryptography.Pkcs",
                 "System.Security.Cryptography.Xml",
                 "System.Threading.RateLimiting",
@@ -306,7 +305,6 @@ static TestData()
                 { "Microsoft.JSInterop" },
                 { "Microsoft.Net.Http.Headers" },
                 { "System.Diagnostics.EventLog" },
-                { "System.Net.ServerSentEvents" },
                 { "System.Security.Cryptography.Xml" },
                 { "System.Threading.RateLimiting" },
             };

src/Http/Http.Results/src/Microsoft.AspNetCore.Http.Results.csproj

@@ -28,7 +28,6 @@
     <Reference Include="Microsoft.AspNetCore.Hosting.Abstractions" />
     <Reference Include="Microsoft.AspNetCore.Http.Extensions" />
     <Reference Include="Microsoft.AspNetCore.Routing" />
-    <Reference Include="System.Net.ServerSentEvents" />
 
     <InternalsVisibleTo Include="Microsoft.AspNetCore.Http.Results.Tests" />
   </ItemGroup>