ttrpc-codegen: Update dependence ttrpc-compiler to 0.4.0

Since ttrpc-codegen 0.2.0 should use compiler 0.4.0 to
generate ttrpc 0.5.0 code.

And I have just published the ttrpc-compiler 0.4.0

Signed-off-by: Tim Zhang <tim@hyper.sh>

Author: Tim-Zhang

ttrpc-codegen/Cargo.toml

@@ -16,4 +16,4 @@ readme = "README.md"
 protobuf = { version = "2.14.0" }
 protobuf-codegen-pure = "2.14.0"
 protobuf-codegen = "2.14.0"
-ttrpc-compiler = "0.3.2"
+ttrpc-compiler = "0.4.0"