chore: regenerate README versions (#124)

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README.md

@@ -17,7 +17,7 @@ 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>5.5.0</version>
+      <version>5.7.0</version>
       <type>pom</type>
       <scope>import</scope>
     </dependency>

synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-billing.git",
-        "sha": "df9c38667eb2d83c01b40ad916506cb6e84a7390"
+        "sha": "36d1072109bc01ef8db4c9aa9f6aa8a9d45f8920"
       }
     },
     {