remove bom

Author: JoeWang1127

java-sdk-logging/java-sdk-logging-extensions-bom/pom.xml

@@ -13,7 +13,6 @@
     <relativePath>../gapic-generator-java-pom-parent</relativePath>
   </parent>
   <modules>
-    <module>java-sdk-logging-extensions-bom</module>
     <module>log4j2-extension</module>
     <module>logback-extension</module>
   </modules>