Fix error when creating a transaction in bookshop-srv (MT)

Adds org.apache.commons:commons-collections4:4.4 as dependency. The dependency is needed for com.sap.cds:cds-feature-mt:3.4.0 but never imported.
This is likely a bug.

Author: maginseb

srv/pom.xml

@@ -22,6 +22,12 @@
 			<artifactId>cds-starter-spring-boot</artifactId>
 		</dependency>
 
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-collections4</artifactId>
+            <version>4.4</version>
+        </dependency>
+
 		<dependency>
 			<groupId>com.sap.cds</groupId>
 			<artifactId>cds-adapter-odata-v4</artifactId>