Update mcr.microsoft.com/dotnet/runtime Docker tag to v7

Author: renovate[bot]

Dockerfile

@@ -28,7 +28,7 @@ RUN \
   dotnet publish -o output/ -r "${ARCH}" -v m -f net6.0 -c Release -p:PublishSingleFile=true --self-contained false
 
 # Runtime image
-FROM --platform=${TARGETPLATFORM} mcr.microsoft.com/dotnet/runtime:6.0 AS runner
+FROM --platform=${TARGETPLATFORM} mcr.microsoft.com/dotnet/runtime:7.0 AS runner
 WORKDIR /server
 COPY --from=builder /TShock/TShockLauncher/output ./