minor: remove redundant prefix

[jackwener]

Which issue does this PR close?

Closes #.

Rationale for this change

When I read source code about Arrow-flight, find some redundant prefix

What changes are included in this PR?

Are there any user-facing changes?

[jackwener]

Don't understand why CI reports an error, is it because these codes are not allowed to change?

[tustvold]

is it because these codes are not allowed to change

arrow.flight.protocol.rs and arrow.flight.protocol.sql.rs are auto-generated and shouldn't be altered manually

[ursabot]

Benchmark runs are scheduled for baseline = 3a90654 and contender = 3db7f42. 3db7f42 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