[tex-eplain] update for CTAN lion file location

[Van Ly]

Hello,

The CTAN lion file is located at [1].  The Makefile at [2] lists an 
invalid location.

 	Van Ly

[1] https://www.ctan.org/lion/files/ctan_lion_350x350.png
[2] http://tug.org/eplain/demo/Makefile

The \fmtversion is as follows for the one that I have.

\fmtversion{3.9: 30 May 2019 (and plain \plainversion)}

-- 
... dragons do not see stones, fish do not see water.