chore: fix sideinput-udf image build

[BulkBeing]

The image build started failing after the changes for using cargo workspaces:

  ./hack/update_examples.sh --build-push-example examples/sideinput/udf
  shell: /usr/bin/bash -e {0}
Using tag: stable
cargo check
error: current package believes it's in a workspace when it's not:
current:   /home/runner/work/numaflow-rs/numaflow-rs/examples/sideinput/udf/Cargo.toml
workspace: /home/runner/work/numaflow-rs/numaflow-rs/Cargo.toml

this may be fixable by adding `examples/sideinput/udf` to the `workspace.members` array of the manifest located at: /home/runner/work/numaflow-rs/numaflow-rs/Cargo.toml
Alternatively, to keep it out of the workspace, add the package to the `workspace.exclude` array, or add an empty `[workspace]` table to the package's manifest.
make: *** [Makefile:8: update] Error 101
Error: failed to run make image in examples/sideinput/udf
Error: Process completed with exit code 1.