[ThinLTO/gold] Remove thin archive part of new test due to bot failures

I am getting a bot failure from the thin archive part of this test:

From
http://bb.pgr.jp/builders/cmake-llvm-x86_64-linux/builds/40468/steps/test_llvm/logs/LLVM%20%3A%3A%20tools__gold__X86__thinlto_emit_linked_objects.ll:

Command Output (stderr):
--
/home/bb/cmake-llvm-x86_64-linux/build/./bin/llvm-ar: creating
/home/bb/cmake-llvm-x86_64-linux/build/test/tools/gold/X86/Output/thinlto_emit_linked_objects.ll.tmp2.a
/usr/bin/ld.gold: internal error in add_writer, at
../../gold/token.h:124

--

This appears to be an issue with an older version of gold. The test case
passes for me locally when I use the gold v1.12 I was testing with, but
when I tried the gold installed on my system which is v1.11 I get the
same error.

Remove the thin archive version of the test, since there isn't a way to
predicate it on gold version.

llvm-svn: 276453