math/lapack: fix broken lib symlink

In lapack-3.10.0, there is a broken sym link for libtmglib.so.3.10.0
(should be a file):

/usr/local/lib/libtmglib.so.3@ -> libtmglib.so.3.10.0
/usr/local/lib/libtmglib.so.3.10.0@ -> libtmglib.so.3

Just remove the unnecessary code in post-install for libtmglib shared
lib files. 'do-install' does everything correctly.

PR: 257139
Reported by: John Hein <jcfyecrayz (at) liamekaens.com>