chore: regenerate README (#404)

This PR was generated using Autosynth. 🌈


<details><summary>Log from Synthtool</summary>

```
2021-02-26 17:46:52,816 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-securitycenter/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-02-26 17:46:54,426 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

```
</details>

Full log will be available here:
https://source.cloud.google.com/results/invocations/5f675bc3-1aa3-4609-afdc-c44148411769/targets

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Author: yoshi-automation

.github/readme/synth.metadata/synth.metadata

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-securitycenter.git",
-        "sha": "6ed61e3fef3f212a1442bd8579f8024f94b6fbba"
+        "sha": "d292fe47b30d1595cc587f18ae41968c3dd9c5ab"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "0199c79b8324fba66476300824aa931788c47e2d"
+        "sha": "8c5628b86cfa8386de7b8fc1675e6b528b552d57"
       }
     }
   ]

README.md

@@ -56,12 +56,12 @@ compile 'com.google.cloud:google-cloud-securitycenter'
 ```
 If you are using Gradle without BOM, add this to your dependencies
 ```Groovy
-compile 'com.google.cloud:google-cloud-securitycenter:1.3.7'
+compile 'com.google.cloud:google-cloud-securitycenter:1.3.8'
 ```
 
 If you are using SBT, add this to your dependencies
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-securitycenter" % "1.3.7"
+libraryDependencies += "com.google.cloud" % "google-cloud-securitycenter" % "1.3.8"
 ```
 
 ## Authentication