[minor] fix doc test fail

[Ted-Jiang]

Which issue does this PR close?

Closes #.

Rationale for this change

run doc test in clion got error

/Users/yangjiang/.cargo/bin/cargo test --color=always --doc "array::union_array::UnionArray\ (line\ 42)" --no-fail-fast --manifest-path /Users/yangjiang/github/arrow-rs/arrow-array/Cargo.toml -- --format=json -Z unstable-options --show-output
Testing started at 16:48 ...
   Compiling arrow-array v33.0.0 (/Users/yangjiang/github/arrow-rs/arrow-array)
    Finished test [unoptimized + debuginfo] target(s) in 0.90s
   Doc-tests arrow_array
warning: use of deprecated associated function `arrow_array::FixedSizeBinaryArray::try_from_sparse_iter`: This function will fail if the iterator produces only None values; prefer `try_from_sparse_iter_with_size`
 --> src/array/fixed_size_binary_array.rs:45:36
  |
6 |    let arr = FixedSizeBinaryArray::try_from_sparse_iter(input_arg.into_iter()).unwrap();
  |                                    ^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(deprecated)]` on by default

warning: 1 warning emitted

Test executable failed (exit status: 101).

What changes are included in this PR?

Are there any user-facing changes?

[ursabot]

Benchmark runs are scheduled for baseline = ea48b95 and contender = 9a6c516. 9a6c516 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ursa-thinkcentre-m75q] ursa-thinkcentre-m75q
Buildkite builds:
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java