chore: regenerate README (#453)

This PR was generated using Autosynth. 🌈


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

```
2021-02-26 01:26:17,894 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-logging/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-02-26 01:26:19,545 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/8805b719-749b-4874-ac5c-8f403008c3dd/targets

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

Author: yoshi-automation

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

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-logging.git",
-        "sha": "ab86346f38df830ba9b8e45b36fe4fcd52b7dd81"
+        "sha": "35749a1291c979c7448c777af3f637e590320f3b"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "0199c79b8324fba66476300824aa931788c47e2d"
+        "sha": "8c5628b86cfa8386de7b8fc1675e6b528b552d57"
       }
     }
   ]

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-logging</artifactId>
-  <version>2.1.4</version>
+  <version>2.1.5</version>
 </dependency>
 
 ```
@@ -52,12 +52,12 @@ compile 'com.google.cloud:google-cloud-logging'
 ```
 If you are using Gradle without BOM, add this to your dependencies
 ```Groovy
-compile 'com.google.cloud:google-cloud-logging:2.1.4'
+compile 'com.google.cloud:google-cloud-logging:2.1.5'
 ```
 
 If you are using SBT, add this to your dependencies
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-logging" % "2.1.4"
+libraryDependencies += "com.google.cloud" % "google-cloud-logging" % "2.1.5"
 ```
 
 ## Authentication