ld.config.txt: remove link from rs to vndk

Linker namespace 'rs' has /system/lib/vndk-sp in its search paths.
So we don't need to link 'rs' namespace to 'vndk' namespace.

Bug: 139706981
Test: run RS-using apps from Play
Change-Id: I14c1d6c4e7624bbd6551731ea88de1b4c2e5edb6