[llvm] [CFGMST] Remove special case for entry block with no successors (PR #140804)

[Ellis Hoag via llvm-commits]

================
@@ -0,0 +1,13 @@
+; RUN: llvm-profdata merge %S/Inputs/unreachable-block.proftext -o %t.profdata
----------------
ellishg wrote:

Please use `split-file` so that the `.proftext` file is inline in this test

https://llvm.org/docs/TestingGuide.html#extra-files

https://github.com/llvm/llvm-project/pull/140804