Fix Rscript displays initial messages.

[koba-z33]

In R, the "--slave" option has been changed to the "--no-echo" option, so in MRO 4.0.2, Rscript will display the initial message.

https://stat.ethz.ch/pipermail/r-help/2019-September/464281.html

The following bugs have been fixed.

[vagrant@localhost ropen]$ /opt/microsoft/ropen/3.5.3/lib64/R/bin/Rscript -e "1 + 2"
[1] 3
[vagrant@localhost ropen]$ /opt/microsoft/ropen/4.0.2/lib64/R/bin/Rscript -e "1 + 2"
Microsoft R Open 4.0.2
The enhanced R distribution from Microsoft
Microsoft packages Copyright (C) 2020 Microsoft Corporation

Using the Intel MKL for parallel mathematical computing (using 4 cores).

Default CRAN mirror snapshot taken on 2020-07-16.
See: https://mran.microsoft.com/.

[1] 3
[vagrant@localhost ropen]$ 

[free-variation]

This is a useful PR -- it's been more than a month. Are there still devs on this project?