Upgrade to AssertJ 3.26.3

Closes: #135

Author: mdeinum

spring-batch-excel/pom.xml

@@ -48,7 +48,7 @@
         <poi.version>5.3.0</poi.version>
 
 		<!-- Test Dependencies -->
-		<assertj.version>3.18.1</assertj.version>
+		<assertj.version>3.26.3</assertj.version>
 		<junit.jupiter.version>5.10.2</junit.jupiter.version>
 		<slf4j.version>1.7.36</slf4j.version>
 		<mockito.version>5.12.0</mockito.version>