MINOR: [C++] Remove nonexistent class from io/type_fwd.h

[lidavidm]

No description provided.

[ursabot]

Benchmark runs are scheduled for baseline = d4f6088 and contender = f3af96a. f3af96a is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Finished ⬇️0.0% ⬆️0.0%] ec2-t3-xlarge-us-east-2
[Failed ⬇️0.24% ⬆️0.0%] test-mac-arm
[Failed ⬇️0.0% ⬆️0.0%] ursa-i9-9960x
[Finished ⬇️0.07% ⬆️0.0%] ursa-thinkcentre-m75q
Buildkite builds:
[Finished] f3af96a2 ec2-t3-xlarge-us-east-2
[Failed] f3af96a2 test-mac-arm
[Failed] f3af96a2 ursa-i9-9960x
[Finished] f3af96a2 ursa-thinkcentre-m75q
[Finished] d4f6088a ec2-t3-xlarge-us-east-2
[Finished] d4f6088a test-mac-arm
[Failed] d4f6088a ursa-i9-9960x
[Finished] d4f6088a 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