java: need to exclude google-cloud-bom and libraries-bom from gapic-libraries-bom/pom.xml

[zhumin8]

PR in google-cloud-java that merges libraries bom into monorepo breaks the generation. See details below

First failed run from bom migrate PR: googleapis/google-cloud-java#13498
I believe google-cloud-bom and libraries-bom should not be in gapic-libraries-bom. Needs change in librarian. The current (and old hermetic build logic) adds all -pom modules to it.

diff --git a/gapic-libraries-bom/pom.xml b/gapic-libraries-bom/pom.xml
index abf38236727..e4e0d2ee785 100644
--- a/gapic-libraries-bom/pom.xml
+++ b/gapic-libraries-bom/pom.xml
@@ -336,6 +336,13 @@
         <type>pom</type>
         <scope>import</scope>
       </dependency>
+      <dependency>
+        <groupId>com.google.cloud</groupId>
+        <artifactId>google-cloud-bom</artifactId>
+        <version>0.266.0-SNAPSHOT</version><!-- {x-version-update:google-cloud:current} -->
+        <type>pom</type>
+        <scope>import</scope>
+      </dependency>
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>google-cloud-build-bom</artifactId>
@@ -1543,6 +1550,13 @@
         <type>pom</type>
         <scope>import</scope>
       </dependency>
+      <dependency>
+        <groupId>com.google.cloud</groupId>
+        <artifactId>libraries-bom</artifactId>
+        <version>26.85.0-SNAPSHOT</version><!-- {x-version-update:libraries:current} -->
+        <type>pom</type>
+        <scope>import</scope>
+      </dependency>
       <dependency>
         <groupId>io.grafeas</groupId>
         <artifactId>grafeas</artifactId>

Originally posted by @zhumin8 in #13609

[zhumin8]

Fix by adding these two modules to excludedBOMs.
Followup: maybe making this a config in librarian.yaml instead of hardcoded. Not a high priority as I don't foresee any more BOM added into google-cloud-java.