update guava and GAX (#71)

Author: elharo

pom.xml

@@ -133,7 +133,11 @@
         <artifactId>google-api-services-storage</artifactId>
         <version>v1-rev20191011-1.30.3</version>
       </dependency>
-
+      <dependency>
+        <groupId>com.google.guava</groupId>
+        <artifactId>guava</artifactId>
+        <version>28.2-android</version>
+      </dependency>
       <dependency>
         <groupId>org.checkerframework</groupId>
         <artifactId>checker-compat-qual</artifactId>