THRIFT-5684 upgrade to net7.0:
Client: netstd
Patch: Jens Geyer
diff --git a/build/docker/old/debian-stretch/Dockerfile b/build/docker/old/debian-stretch/Dockerfile
index 628b626..25237ca 100644
--- a/build/docker/old/debian-stretch/Dockerfile
+++ b/build/docker/old/debian-stretch/Dockerfile
@@ -102,10 +102,10 @@
# project isn't ready for this quite yet:
# RUN apt-get install -y --no-install-recommends \
# `# dotnet core dependencies` \
-# dotnet-sdk-6.0 \
-# dotnet-runtime-6.0 \
-# aspnetcore-runtime-6.0 \
-# dotnet-apphost-pack-6.0
+# dotnet-sdk-7.0 \
+# dotnet-runtime-7.0 \
+# aspnetcore-runtime-7.0 \
+# dotnet-apphost-pack-7.0
RUN apt-get install -y --no-install-recommends \
`# Erlang dependencies` \