[llvm-readobj/llvm-readelf] - Eliminate the elf-groups.x86_64 precompiled binary from the inputs.

We do not need the elf-groups.x86_64. In one of the tests, it was
used for no solid reason, and for the second test case we can use
YAML input with SHT_GROUP sections.

The patch performs a cleanup of one of the test cases, removes another
one completely (since during the review was found out it actually
duplicates one of the existent tests) and removes the precompiled binary.

Differential revision: https://reviews.llvm.org/D63647

llvm-svn: 364167