Upgrade dotnet sdk to v6.0.420 (#3211)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

src/dev.sh

@@ -17,7 +17,7 @@ LAYOUT_DIR="$SCRIPT_DIR/../_layout"
 DOWNLOAD_DIR="$SCRIPT_DIR/../_downloads/netcore2x"
 PACKAGE_DIR="$SCRIPT_DIR/../_package"
 DOTNETSDK_ROOT="$SCRIPT_DIR/../_dotnetsdk"
-DOTNETSDK_VERSION="6.0.419"
+DOTNETSDK_VERSION="6.0.420"
 DOTNETSDK_INSTALLDIR="$DOTNETSDK_ROOT/$DOTNETSDK_VERSION"
 RUNNER_VERSION=$(cat runnerversion)
 

src/global.json

@@ -1,5 +1,5 @@
 {
   "sdk": {
-    "version": "6.0.419"
+    "version": "6.0.420"
   }
 }