remove default framework in perf setup script (#79258)

* remove default framework in perf setup script

* remove default framework in perf setup script

Author: kasperk81

eng/testing/performance/performance-setup.ps1

@@ -3,7 +3,7 @@ Param(
     [string] $CoreRootDirectory,
     [string] $BaselineCoreRootDirectory,
     [string] $Architecture="x64",
-    [string] $Framework="net5.0",
+    [string] $Framework,
     [string] $CompilationMode="Tiered",
     [string] $Repository=$env:BUILD_REPOSITORY_NAME,
     [string] $Branch=$env:BUILD_SOURCEBRANCH,

eng/testing/performance/performance-setup.sh

@@ -7,7 +7,7 @@ source_directory=$BUILD_SOURCESDIRECTORY
 core_root_directory=
 baseline_core_root_directory=
 architecture=x64
-framework=net5.0
+framework=
 compilation_mode=tiered
 repository=$BUILD_REPOSITORY_NAME
 branch=$BUILD_SOURCEBRANCH