Remove the old ARM code generator from ART's Optimizing compiler.

The AArch32 VIXL-based code generator has been the default
ARM code generator in ART for some time now. The old ARM
code generator does not compile anymore; retiring it.

Test: test.py
Bug: 63316036
Change-Id: Iab8fbc4ac73eac2c1a809cd7b22fec6b619755db
diff --git a/compiler/optimizing/instruction_simplifier_shared.cc b/compiler/optimizing/instruction_simplifier_shared.cc
index e5a8499..d1bc4da 100644
--- a/compiler/optimizing/instruction_simplifier_shared.cc
+++ b/compiler/optimizing/instruction_simplifier_shared.cc
@@ -274,8 +274,8 @@
   // `HArm64Load` and `HArm64Store`,`HArmLoad` and `HArmStore`). We defer these changes
   // because these new instructions would not bring any advantages yet.
   // Also see the comments in
-  // `InstructionCodeGeneratorARM::VisitArrayGet()`
-  // `InstructionCodeGeneratorARM::VisitArraySet()`
+  // `InstructionCodeGeneratorARMVIXL::VisitArrayGet()`
+  // `InstructionCodeGeneratorARMVIXL::VisitArraySet()`
   // `InstructionCodeGeneratorARM64::VisitArrayGet()`
   // `InstructionCodeGeneratorARM64::VisitArraySet()`.
   return true;