vendor: update github.com/dropbox/dropbox-sdk-go-unofficial

vendor/github.com/dropbox/dropbox-sdk-go-unofficial/generator/generate-sdk.sh

@@ -1,7 +1,7 @@
 #! /usr/bin/env bash
 set -euo pipefail
 
-if [[ $# -ne 0 ]]; then
+if [[ $# -gt 1 ]]; then
     echo "$0: Not expecting any command-line arguments, got $#." 1>&2
     exit 1
 fi
@@ -15,7 +15,7 @@ stone -v -a :all go_types.stoneg.py "$gen_dir" "$spec_dir"/*.stone
 stone -v -a :all go_client.stoneg.py "$gen_dir" "$spec_dir"/*.stone
 
 # Update SDK and API spec versions
-sdk_version="1.0.0-beta"
+sdk_version=${1:-"1.0.0-beta"}
 pushd ${spec_dir}
 spec_version=$(git rev-parse --short HEAD)
 popd