Fix incorrect classname in DLP Generated Client Documentation. (#1560)

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.

```

Dlp/src/V2/Gapic/DlpServiceGapicClient.php

@@ -28,12 +28,12 @@
 
 use Google\ApiCore\ApiException;
 use Google\ApiCore\CredentialsWrapper;
-use Google\ApiCore\FetchAuthTokenInterface;
 use Google\ApiCore\GapicClientTrait;
 use Google\ApiCore\PathTemplate;
 use Google\ApiCore\RetrySettings;
 use Google\ApiCore\Transport\TransportInterface;
 use Google\ApiCore\ValidationException;
+use Google\Auth\FetchAuthTokenInterface;
 use Google\Cloud\Dlp\V2\ByteContentItem;
 use Google\Cloud\Dlp\V2\CancelDlpJobRequest;
 use Google\Cloud\Dlp\V2\ContentItem;

Dlp/synth.metadata

@@ -1,26 +1,31 @@
 {
+  "updateTime": "2018-12-18T11:00:41.167316Z",
   "sources": [
     {
-      "git": {
-        "name": "googleapis",
-        "remote": "https://github.com/googleapis/googleapis.git",
-        "sha": "5a57f0c13a358b2b15452bf2d67453774a5f6d4f",
-        "internalRef": "221837528"
+      "generator": {
+        "name": "artman",
+        "version": "0.16.3",
+        "dockerImage": "googleapis/artman@sha256:bfb92654b4a77368471f70e2808eaf4e60f263b9559f27bb3284097322787bf1"
       }
     },
     {
       "git": {
-        "name": "googleapis-private",
-        "remote": "https://github.com/googleapis/googleapis-private.git",
-        "sha": "6aa8e1a447bb8d0367150356a28cb4d3f2332641",
-        "internalRef": "221340946"
+        "name": "googleapis",
+        "remote": "https://github.com/googleapis/googleapis.git",
+        "sha": "c04bc0dc0a9164d924a9ab923fd6845b4ae6a7ab",
+        "internalRef": "225851467"
       }
-    },
+    }
+  ],
+  "destinations": [
     {
-      "generator": {
-        "name": "artman",
-        "version": "0.16.0",
-        "dockerImage": "googleapis/artman@sha256:90f9d15e9bad675aeecd586725bce48f5667ffe7d5fc4d1e96d51ff34304815b"
+      "client": {
+        "source": "googleapis",
+        "apiName": "dlp",
+        "apiVersion": "v2",
+        "language": "php",
+        "generator": "gapic",
+        "config": "google/privacy/dlp/artman_dlp_v2.yaml"
       }
     }
   ]