Fix incorrect classname in DLP Generated Client Documentation.

[yoshi-automation]

This PR was generated using Autosynth. 🌈

Here's the log from Synthtool:

synthtool > Executing /tmpfs/src/git/autosynth/working_repo/Dlp/synth.py.
synthtool > Ensuring dependencies.
synthtool > Pulling artman image.
latest: Pulling from googleapis/artman
Digest: sha256:bfb92654b4a77368471f70e2808eaf4e60f263b9559f27bb3284097322787bf1
Status: Image is up to date for googleapis/artman:latest
synthtool > Cloning googleapis.
synthtool > Running generator for google/privacy/dlp/artman_dlp_v2.yaml.
synthtool > Generated code into /home/kbuilder/.cache/synthtool/googleapis/artman-genfiles/php/google-cloud-dlp-v2.
synthtool > Replaced 'Copyright \\d{4}' in src/V2/Gapic/DlpServiceGapicClient.php.
synthtool > Replaced 'Copyright \\d{4}' in src/V2/DlpServiceClient.php.
synthtool > Replaced 'Copyright \\d{4}' in tests/Unit/V2/DlpServiceClientTest.php.
synthtool > Replaced '@type InspectJobConfig \\$inspectJob\\n' in src/V2/Gapic/DlpServiceGapicClient.php.
synthtool > Replaced '@type RiskAnalysisJobConfig \\$riskJob\\n' in src/V2/Gapic/DlpServiceGapicClient.php.
synthtool > Replaced 'RedactImageRequest_ImageRedactionConfig' in src/V2/Gapic/DlpServiceGapicClient.php.
synthtool > Cleaned up 1 temporary directories.
synthtool > Wrote metadata to synth.metadata.