Revert^4 "Compiler changes for bitstring based type checks."

Disabled the build time flag. (No image version bump needed.)

Bug: 26687569
Bug: 64692057
Bug: 76420366

This reverts commit 3fbd3ad99fad077e5c760e7238bcd55b07d4c06e.

Change-Id: I5d83c4ce8a7331c435d5155ac6e0ce1c77d60004
diff --git a/compiler/optimizing/code_generator.h b/compiler/optimizing/code_generator.h
index a487320..3bd5e14 100644
--- a/compiler/optimizing/code_generator.h
+++ b/compiler/optimizing/code_generator.h
@@ -438,6 +438,8 @@
       case TypeCheckKind::kArrayCheck:
       case TypeCheckKind::kUnresolvedCheck:
         return false;
+      case TypeCheckKind::kBitstringCheck:
+        return true;
     }
     LOG(FATAL) << "Unreachable";
     UNREACHABLE();