pom.xml: guava 26.0-android

27.0-android contains bug google/guava#3302, causing Android builds to fail

Author: fxnn

pom.xml

@@ -46,7 +46,7 @@
             <!-- NOTE: Use android version for JDK7/Android compatibility -->
             <groupId>com.google.guava</groupId>
             <artifactId>guava</artifactId>
-            <version>27.0-android</version>
+            <version>26.0-android</version>
         </dependency>
         <dependency>
             <groupId>commons-io</groupId>