GH-35911: [Go] Fix method CastToBytes of decimal256Traits

[izveigor]

Rationale for this change

What changes are included in this PR?

Are these changes tested?

Yes

Are there any user-facing changes?

Yes

• Closes: method CastToBytes of decimal256Traits does not work #35911

[github-actions]

⚠️ GitHub issue #35911 has been automatically assigned in GitHub to PR creator.

[zeroshade]

Good catch! Thanks!

[ursabot]

Benchmark runs are scheduled for baseline = 3d0172d and contender = 4ec231b. 4ec231b is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Failed] ec2-t3-xlarge-us-east-2
[Failed ⬇️0.74% ⬆️0.03%] test-mac-arm
[Finished ⬇️0.0% ⬆️0.0%] ursa-i9-9960x
[Failed ⬇️0.27% ⬆️0.0%] ursa-thinkcentre-m75q
Buildkite builds:
[Failed] 4ec231b2 ec2-t3-xlarge-us-east-2
[Failed] 4ec231b2 test-mac-arm
[Finished] 4ec231b2 ursa-i9-9960x
[Failed] 4ec231b2 ursa-thinkcentre-m75q
[Failed] 3d0172d4 ec2-t3-xlarge-us-east-2
[Failed] 3d0172d4 test-mac-arm
[Finished] 3d0172d4 ursa-i9-9960x
[Failed] 3d0172d4 ursa-thinkcentre-m75q
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