Fix logical merge conflict: match arms have incompatible types

[alamb]

Fix build on master

I merged #2094 which had a logical conflict which results in a build failure on master such as https://github.com/apache/arrow-rs/runs/7455984487?check_suite_focus=true

   Compiling arrow-integration-testing v18.0.0 (/__w/arrow-rs/arrow-rs/integration-testing)
error[E0308]: `match` arms have incompatible types
   --> integration-testing/src/lib.rs:645:26
    |
628 | /                 match is_valid {
629 | |                     1 => {
630 | |                         let str = value.as_str().unwrap();
631 | |                         let integer = BigInt::parse_bytes(str.as_bytes(), 10).unwrap();
...   |
643 | |                         b.append_value(&decimal)
    | |                         ------------------------ this is found to be of type `std::result::Result<(), ArrowError>`
644 | |                     }
645 | |                     _ => b.append_null(),
    | |                          ^^^^^^^^^^^^^^^ expected enum `std::result::Result`, found `()`
646 | |                 }?;
    | |_________________- `match` arms have incompatible types
    |
    = note:   expected enum `std::result::Result<(), ArrowError>`
            found unit type `()`

[alamb]

I plan to merge this PR once the build step passes

[ursabot]

Benchmark runs are scheduled for baseline = 1805b30 and contender = db91031. db91031 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