feat(rust): use symlink for trezor-client/protob

to satisfy cargo publish --dry-run

it seems there is something smart going on and the symlink is expanded
to file copies during the build

[no changelog]

rust/trezor-client/build.rs

@@ -1,7 +1,7 @@
 use std::{fs, path::PathBuf};
 
 fn main() {
-    let proto_path = "../../common/protob";
+    let proto_path = "protob";
     let protos: Vec<PathBuf> = fs::read_dir(proto_path)
         .unwrap()
         .filter_map(|entry| {

rust/trezor-client/protob

@@ -0,0 +1 @@
+../../common/protob