Move a regression test out of CI (dotnet#80399)

Co-authored-by: Bruce Forstall <brucefo@microsoft.com>

Author: cshung

src/tests/GC/Regressions/Github/Runtime_76219/Runtime_76219.csproj

@@ -2,6 +2,8 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <Optimize>True</Optimize>
+    <!-- Move it out of CI for 78899 -->
+    <CLRTestPriority>1</CLRTestPriority>
 
     <!-- This test needs GCStress mode but it doesn't take long to execute
          so is fine to keep it in the inner loop -->

src/tests/issues.targets

@@ -63,6 +63,9 @@
         <ExcludeList Include="$(XunitTestBinBase)/Interop/MonoAPI/**">
             <Issue>CoreCLR does not implement the mono embedding API</Issue>
         </ExcludeList>
+        <ExcludeList Include="$(XunitTestBinBase)/GC/Regressions/Github/Runtime_76219/Runtime_76219/*">
+            <Issue>https://github.com/dotnet/runtime/issues/78899</Issue>
+        </ExcludeList>
     </ItemGroup>
 
     <!-- All Unix targets on all runtimes -->