MIPS: cleanup api callbacks now that handles are never returned directly

src/mips/macro-assembler-mips.h

Index: src/mips/macro-assembler-mips.h
diff --git a/src/mips/macro-assembler-mips.h b/src/mips/macro-assembler-mips.h
index 3b3cfdb8acf80deb52b0f4bf1ae10090601d29ee..9605038f88f86a8022f8a93eeb3da76f967cdda1 100644
--- a/src/mips/macro-assembler-mips.h
+++ b/src/mips/macro-assembler-mips.h
@@ -1233,7 +1233,6 @@ class MacroAssembler: public Assembler {
                                 ExternalReference thunk_ref,
                                 Register thunk_last_arg,
                                 int stack_space,
-                                bool returns_handle,
                                 int return_value_offset_from_fp);
 
   // Jump to the builtin routine.