fix: handle binary data in GoogleCloudFileStore.write

[rbren]

The write operation in GoogleCloudFileStore accepts bytes or string input, but currently fails when given bytes. This PR fixes the issue by using the appropriate mode (wb for bytes, w for strings) when opening the blob for writing.

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To run this PR locally, use the following command:

docker run -it --rm   -p 3000:3000   -v /var/run/docker.sock:/var/run/docker.sock   --add-host host.docker.internal:host-gateway   -e SANDBOX_RUNTIME_CONTAINER_IMAGE=docker.all-hands.dev/all-hands-ai/runtime:ccddd6c-nikolaik   --name openhands-app-ccddd6c   docker.all-hands.dev/all-hands-ai/openhands:ccddd6c

[amanape]

Makes sense