Stop using `group_static_libs` property

This property is now ignored, so there is no need to set it.
For more details, see the bug and/or "Effecient archive file handling"
in https://lld.llvm.org/NewLLD.html#key-concepts

Bug: 189475744
Test: Manual build succeeds
Change-Id: I79ff6aaba47fb13548d735b291da0796d416be48