HADOOP-17109. add guava BaseEncoding to illegalClasses (#2703)

Signed-off-by: Akira Ajisaka <aajisaka@apache.org>

hadoop-build-tools/src/main/resources/checkstyle/checkstyle.xml

@@ -122,7 +122,7 @@
         <module name="IllegalImport">
           <property name="regexp" value="true"/>
           <property name="illegalPkgs" value="sun, com\.google\.common"/>
-          <property name="illegalClasses" value="^org\.apache\.hadoop\.thirdparty\.com\.google\.common\.base\.(Optional|Function|Predicate|Supplier), ^org\.apache\.hadoop\.thirdparty\.com\.google\.common\.collect\.(ImmutableListMultimap)"/>
+          <property name="illegalClasses" value="^org\.apache\.hadoop\.thirdparty\.com\.google\.common\.io\.BaseEncoding, ^org\.apache\.hadoop\.thirdparty\.com\.google\.common\.base\.(Optional|Function|Predicate|Supplier), ^org\.apache\.hadoop\.thirdparty\.com\.google\.common\.collect\.(ImmutableListMultimap)"/>
         </module>
         <module name="RedundantImport"/>
         <module name="UnusedImports"/>