chore: regenerate README (#586)

This PR was generated using Autosynth. 🌈


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

```
2021-05-27 18:44:07,843 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-containeranalysis/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-05-27 18:44:08,958 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/6917785b-1fc1-4f34-b7b5-b45222275e0c/targets

- [ ] To automatically regenerate this PR, check this box. (May take up to 24 hours.)

Author: yoshi-automation

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-containeranalysis.git",
-        "sha": "8c19825cd2960db6565002b32f6782dd8f1a4f0c"
+        "sha": "043d026e2cd09f3dfdd753c805f01e4e977a7f83"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "1778de119522ea9c9b18763c2a4577e22a60433c"
+        "sha": "d543abd7c1f500bdbe530a35ca174ee374fde8f6"
       }
     }
   ]

README.md

@@ -38,7 +38,7 @@ If you are using Maven without BOM, add this to your dependencies:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-containeranalysis</artifactId>
-  <version>1.3.0</version>
+  <version>1.3.1</version>
 </dependency>
 
 ```