Update framework to net8.0. (#78012)

Author: cincuranet

eng/pipelines/coreclr/templates/perf-job.yml

@@ -5,7 +5,7 @@ parameters:
   osSubgroup: ''
   container: ''
   runtimeVariant: ''
-  framework: net7.0 # Specify the appropriate framework when running release branches (ie net6.0 for release/6.0)
+  framework: net8.0 # Specify the appropriate framework when running release branches (ie net6.0 for release/6.0)
   liveLibrariesBuildConfig: ''
   variables: {}
   runtimeType: 'coreclr'