Update reflection.jl (#380)

Author: christiangnrd

src/compiler/reflection.jl

@@ -70,5 +70,5 @@ function return_type(@nospecialize(func), @nospecialize(tt))
     job = CompilerJob(source, config)
     interp = GPUCompiler.get_interpreter(job)
     sig = Base.signature_type(func, tt)
-    Core.Compiler.return_type(interp, sig)
+    Core.Compiler._return_type(interp, sig)
 end