Second attempt to disable instrprof-merging.cpp

The first attempt in f82ae3ad was not handled correctly, as
'UNSUPPORTED: *' is not accepted by lit.

compiler-rt/test/profile/instrprof-merging.disabled

@@ -1,4 +1,3 @@
-// UNSUPPORTED: *
 // 1) Compile shared code into different object files and into an executable.
 
 // RUN: %clangxx_profgen -std=c++14 -fcoverage-mapping %s -c -o %t.v1.o \