chore: regenerate README (googleapis#308)

This PR was generated using Autosynth. 🌈


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

```
2020-11-17 18:33:49,796 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-resourcemanager/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working directory clean
2020-11-17 18:33:50,806 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/e8117cf4-f485-46c6-b608-0952c605c3d3/targets

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

java-resourcemanager/.github/readme/synth.metadata/synth.metadata

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-resourcemanager.git",
-        "sha": "dc52b0e4b64fbb33741c579ab681015eff997abc"
+        "sha": "218e633c695913e4a8f22f1be2891478f09006b3"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "ba9918cd22874245b55734f57470c719b577e591"
+        "sha": "7fcc405a579d5d53a726ff3da1b7c8c08f0f2d58"
       }
     }
   ]

java-resourcemanager/README.md

@@ -20,7 +20,7 @@ If you are using Maven with [BOM][libraries-bom], add this to your pom.xml file
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>libraries-bom</artifactId>
-      <version>13.4.0</version>
+      <version>15.1.0</version>
       <type>pom</type>
       <scope>import</scope>
     </dependency>