Fix excldue typo in apache-rat exclude patterns (#5154)

pom.xml

diff --git a/pom.xml b/pom.xml
index 25882c4..d5ecf43 100644
--- a/pom.xml
+++ b/pom.xml
@@ -236,9 +236,9 @@
             <exclude>DISCLAIMER</exclude>
             <exclude>.travis.yml</exclude>
             <exclude>**/*.md</exclude>
-            <excldue>**/*.MD</excldue>
-            <excldue>**/*.iml</excldue>
-            <excldue>.github/**</excldue>
+            <exclude>**/*.MD</exclude>
+            <exclude>**/*.iml</exclude>
+            <exclude>.github/**</exclude>
             <!-- Skip the code style configuration file -->
             <exclude>**/etc/eclipse-java-google-style.xml</exclude>
             <exclude>**/etc/intellij-java-google-style.xml</exclude>