chore: regenerate README (#388)

This PR was generated using Autosynth. 🌈


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

```
2021-02-24 20:01:36,048 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-secretmanager/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-02-24 20:01:37,618 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/dd4aa96e-d6e6-4320-a7f5-11c9b4185a34/targets

- [ ] To automatically regenerate this PR, check this box.

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

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-secretmanager.git",
-        "sha": "338235758e8e8243bb2cfa75303366b85f619ad1"
+        "sha": "fa1983209471dd2cb7a643aef1208e159cae5727"
       }
     },
     {

README.md

@@ -39,7 +39,7 @@ If you are using Maven without BOM, add this to your dependencies:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-secretmanager</artifactId>
-  <version>1.2.8</version>
+  <version>1.3.0</version>
 </dependency>
 
 ```