[CodeGen] Remove mentions of OLDPM

We stopped testing with -check-prefix=SAMPLEPGO-OLDPM and
-check-prefix=THINLTO-OLDPM as of:

  commit 8a7a280
  Author: Thomas Preud'homme <thomasp@graphcore.ai>
  Date:   Fri Sep 17 10:23:40 2021 +0100

clang/test/CodeGen/pgo-sample-thinlto-summary.c

@@ -14,20 +14,9 @@ void foo(int n) {
 // SAMPLEPGO:               Running pass: PGOIndirectCallPromotion on [module]
 // SAMPLEPGO:               Running pass: LoopUnrollPass on bar
 
-// SAMPLEPGO-OLDPM:         PGOIndirectCallPromotion
-// SAMPLEPGO-OLDPM:         Unroll loops
-// SAMPLEPGO-OLDPM:         Unroll loops
-
 // THINLTO-NOT:             Running pass: PGOIndirectCallPromotion on [module]
 // THINLTO-NOT:             Running pass: LoopUnrollPass on bar
 
-// THINLTO-OLDPM-NOT:       PGOIndirectCallPromotion
-// The first Unroll loop pass is the createSimpleLoopUnrollPass that unrolls and peels
-// loops with small constant trip counts. The second one is skipped by ThinLTO.
-// THINLTO-OLDPM:           Unroll loops
-// THINLTO-OLDPM-NOT:       Unroll loops
-
-
 // Checks if hot call is inlined by normal compile, but not inlined by
 // thinlto compile.
 // SAMPLEPGO-LABEL: define {{(dso_local )?}}void @bar