Revert "Merge pull request #565 from apache/dependabot/maven/org.apache.logging.log4j-log4j-bom-2.22.1"

This reverts commit 8621f5818ff029d828af023af803f05b0aa13366, reversing
changes made to ba889f89c87f5f1ca00fbc47a6555a20649e2a82.

Reason: the build is currently broken and upgrading log4j introduces
more problems.
diff --git a/pom.xml b/pom.xml
index 8a5960e..055e95e 100644
--- a/pom.xml
+++ b/pom.xml
@@ -896,7 +896,7 @@
             <dependency>
                 <groupId>org.apache.logging.log4j</groupId>
                 <artifactId>log4j-bom</artifactId>
-                <version>2.22.1</version>
+                <version>2.20.0</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>