ci: remove unnecessary distributionManagement section (#3565)

The distributionManagement declared in the pom.xml files interferes the
upload to GCP ArtifactRegistry because it tries to
upload artifacts to google.oss.sonatype.org even when you try to upload
artifacts to GCP Artifact Registry (b/377328233#comment9).

The distributionManagement is already configured in the parent POM at

https://github.com/googleapis/java-shared-config/blob/6d526a3129f585338b14dab8f041e56dbaae4cd5/native-image-shared-config/pom.xml#L42.
No need redeclare in these pom.xml files.

java-common-protos/pom.xml

@@ -31,16 +31,6 @@
   <organization>
     <name>Google LLC</name>
   </organization>
-  <distributionManagement>
-    <snapshotRepository>
-      <id>sonatype-nexus-snapshots</id>
-      <url>https://google.oss.sonatype.org/content/repositories/snapshots</url>
-    </snapshotRepository>
-    <repository>
-      <id>sonatype-nexus-staging</id>
-      <url>https://google.oss.sonatype.org/service/local/staging/deploy/maven2/</url>
-    </repository>
-  </distributionManagement>
   <licenses>
     <license>
       <name>Apache-2.0</name>

java-iam/pom.xml

@@ -31,16 +31,6 @@
   <organization>
     <name>Google LLC</name>
   </organization>
-  <distributionManagement>
-    <snapshotRepository>
-      <id>sonatype-nexus-snapshots</id>
-      <url>https://google.oss.sonatype.org/content/repositories/snapshots</url>
-    </snapshotRepository>
-    <repository>
-      <id>sonatype-nexus-staging</id>
-      <url>https://google.oss.sonatype.org/service/local/staging/deploy/maven2/</url>
-    </repository>
-  </distributionManagement>
   <licenses>
     <license>
       <name>Apache-2.0</name>