remove a cppcheck error.

src/targets/gpu/convert.cpp

@@ -14,7 +14,7 @@ shape hip_convert::compute_shape(std::vector<shape> inputs) const
 }
 
 argument hip_convert::compute(context& ctx,
-                              const shape& output_shape,
+                              const shape&, 
                               const std::vector<argument>& args) const
 {
     return device::convert(ctx.get_stream().get(), args[1], args[0]);

src/targets/gpu/include/migraphx/gpu/convert.hpp

@@ -16,7 +16,7 @@ struct hip_convert
     std::string name() const { return "gpu::convert"; }
     shape compute_shape(std::vector<shape> inputs) const;
     argument
-    compute(context& ctx, const shape& output_shape, const std::vector<argument>& args) const;
+    compute(context& ctx, const shape&, const std::vector<argument>& args) const;
     int output_alias(const std::vector<shape>& shapes) const { return shapes.size() - 1; }
 };