remove unused Maven properties and update Guava to 28.0-android (#1351)

* remove unused variable

* remove unused variable and update guava

* update gson

pom.xml

@@ -496,22 +496,20 @@
     <project.http.version>1.31.0</project.http.version>
     <project.oauth.version>1.30.1</project.oauth.version>
     <project.jsr305.version>3.0.2</project.jsr305.version>
-    <project.gson.version>2.1</project.gson.version>
+    <project.gson.version>2.8.5</project.gson.version>
     <project.jackson-core-asl.version>1.9.13</project.jackson-core-asl.version>
     <project.jackson-core2.version>2.9.8</project.jackson-core2.version>
     <project.protobuf-java.version>2.6.1</project.protobuf-java.version>
-    <project.guava.version>26.0-android</project.guava.version>
+    <project.guava.version>28.0-android</project.guava.version>
     <project.appengine.version>1.9.64</project.appengine.version>
     <project.xpp3.version>1.1.4c</project.xpp3.version>
-    <project.commons-logging.version>1.1.1</project.commons-logging.version>
     <project.httpclient.version>4.5.9</project.httpclient.version>
-    <project.httpcore.version>4.4.10</project.httpcore.version>
+    <project.httpcore.version>4.4.11</project.httpcore.version>
     <project.jdo2-api.version>2.3-eb</project.jdo2-api.version>
     <project.datanucleus-core.version>3.2.2</project.datanucleus-core.version>
     <project.datanucleus-api-jdo.version>3.2.1</project.datanucleus-api-jdo.version>
     <project.datanucleus-maven-plugin.version>4.0.3</project.datanucleus-maven-plugin.version>
     <project.servlet-api.version>2.5</project.servlet-api.version>
-    <project.transaction-api.version>1.1</project.transaction-api.version>
     <deploy.autorelease>false</deploy.autorelease>
   </properties>