Update dependencies of test scope

Avoid gap between the versions used by Fake SFTP Server Lambda and the
acutal versions of the dependencies. This avoids that I have to bridge
a large gap once I want to use a new version.

The commit includes the following updates:

commons-io:commons-io .......................... 2.8.0 -> 2.21.0
org.assertj:assertj-core ...................... 3.19.0 -> 3.27.7
org.slf4j:slf4j-nop ........................... 1.7.30 -> 1.7.36

Author: stefanbirkner

pom.xml

@@ -61,13 +61,13 @@
         <dependency>
             <groupId>commons-io</groupId>
             <artifactId>commons-io</artifactId>
-            <version>[2.8.0]</version>
+            <version>[2.21.0]</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
-            <version>[3.19.0]</version>
+            <version>[3.27.7]</version>
             <scope>test</scope>
         </dependency>
         <dependency>
@@ -79,7 +79,7 @@
         <dependency>
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-nop</artifactId>
-            <version>[1.7.30]</version>
+            <version>[1.7.36]</version>
             <scope>test</scope>
         </dependency>
     </dependencies>