chore: regenerate README (#512)

This PR was generated using Autosynth. 🌈


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

```
2021-08-16 22:23:44,231 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-compute/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-08-16 22:23:45,878 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

```
</details>

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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-compute.git",
-        "sha": "f9f56b2675a0dfca55c28c486dabcbea5af52cf9"
+        "sha": "43a9fe10fbb7f9fa64c2d542b40feb419f3e481e"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "3d32990b6f4b57be77455e3ca89e6e21cd0c06b3"
+        "sha": "a01e1a0bf70754f51450958b966bd673945d1e6e"
       }
     }
   ]

README.md

@@ -30,13 +30,13 @@ If you are using Maven, add this to your pom.xml file:
 If you are using Gradle without BOM, add this to your dependencies
 
 ```Groovy
-compile 'com.google.cloud:google-cloud-compute:1.3.0-alpha'
+compile 'com.google.cloud:google-cloud-compute:1.4.0-alpha'
 ```
 
 If you are using SBT, add this to your dependencies
 
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-compute" % "1.3.0-alpha"
+libraryDependencies += "com.google.cloud" % "google-cloud-compute" % "1.4.0-alpha"
 ```
 
 ## Authentication