[maven-release-plugin] prepare release v6.6.0

Author: hiranya911

pom.xml

@@ -19,7 +19,7 @@
 
  <groupId>com.google.firebase</groupId>
  <artifactId>firebase-admin</artifactId>
- <version>6.5.1-SNAPSHOT</version>
+ <version>6.6.0</version>
  <packaging>jar</packaging>
 
  <name>firebase-admin</name>
@@ -66,7 +66,7 @@
  <connection>scm:git:https://github.com/firebase/firebase-admin-java.git</connection>
  <developerConnection>scm:git:ssh://git@github.com/firebase/firebase-admin-java.git</developerConnection>
  <url>http://github.com/firebase/firebase-admin-java</url>
- <tag>HEAD</tag>
+ <tag>v6.6.0</tag>
  </scm>
 
  <distributionManagement>