🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Author: gcf-owl-bot[bot]

README.md

@@ -19,7 +19,7 @@ If you are using Maven with [BOM][libraries-bom], add this to your pom.xml file:
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>libraries-bom</artifactId>
-      <version>26.11.0</version>
+      <version>26.12.0</version>
       <type>pom</type>
       <scope>import</scope>
     </dependency>
@@ -50,7 +50,7 @@ If you are using Maven without the BOM, add this to your dependencies:
 If you are using Gradle 5.x or later, add this to your dependencies:
 
 ```Groovy
-implementation platform('com.google.cloud:libraries-bom:26.11.0')
+implementation platform('com.google.cloud:libraries-bom:26.12.0')
 
 implementation 'com.google.cloud:google-cloud-spanner'
 ```