Remove unused link from postinstall section

Linker ignores link configuration if either namespace is not valid.
However there was a link configuration from postinstall section which
target link namespace does not exist. Also, there was no binary within
postinstall from hwasan build (checked with bonito), so there may be no
usage for this section now. Removing this line for better human
readability, and behavior of the linker would be same as before.

Test: m -j && tested from cuttlefish
Change-Id: I0c7b2949d055ba767e1429238e8764ee7798fe44