chore: regenerate README (#227)

This PR was generated using Autosynth. 🌈


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

```
2020-11-05 02:06:03,537 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-logging-logback/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working directory clean
2020-11-05 02:06:04,459 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/32b563ad-07dd-4d5a-81ed-230d4e3de001/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-logback.git",
-        "sha": "079c51b2dd06107b530517a4a994763fa3557921"
+        "sha": "7c70aa6fb6d9a7e7bb1d7e725cc6ba0067ac1be8"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "ba9918cd22874245b55734f57470c719b577e591"
+        "sha": "3d3e94c4e02370f307a9a200b0c743c3d8d19f29"
       }
     }
   ]

README.md

@@ -79,7 +79,7 @@ See [Logback filters](https://logback.qos.ch/manual/filters.html#thresholdFilter
     <log>application.log</log>
 
     <!-- Optional: defaults to "ERROR" -->
-    <flushLevel>WARN</flushLevel>
+    <flushLevel>WARNING</flushLevel>
 
     <!-- Optional: auto detects on App Engine Flex, Standard, GCE and GKE, defaults to "global". See supported resource types  -->
     <resourceType></resourceType>