Revert "[ubuntu] installing the latest .NET sdk patch version for eve…

…ry feature version (actions#3550)"

This reverts commit a9d832d.

images/linux/scripts/installers/dotnetcore-sdk.sh

@@ -36,8 +36,7 @@ for version in ${DOTNET_VERSIONS[@]}; do
     rm ./${version}.json
 done
 
-sortedSdks=$(echo ${sdks[@]} | tr ' ' '\n' | grep -v preview | grep -v rc | grep -v display | cut -d\" -f2 | sort -r | uniq -w 5)
-
+sortedSdks=$(echo ${sdks[@]} | tr ' ' '\n' | grep -v preview | grep -v rc | grep -v display | cut -d\" -f2 | sort -u -r)
 extract_dotnet_sdk() {
     local ARCHIVE_NAME="$1"
     set -e
@@ -67,4 +66,4 @@ setEtcEnvironmentVariable DOTNET_NOLOGO 1
 setEtcEnvironmentVariable DOTNET_MULTILEVEL_LOOKUP 0
 prependEtcEnvironmentPath '$HOME/.dotnet/tools'
 
-invoke_tests "DotnetSDK"
+invoke_tests "DotnetSDK"