chore: bump rxjava version to 3.1.12

PiperOrigin-RevId: 877872293

Author: tilgalas

a2a/pom.xml

@@ -20,7 +20,6 @@
     <google.adk.version>${project.version}</google.adk.version>
     <guava.version>33.0.0-jre</guava.version>
     <jackson.version>2.19.0</jackson.version>
-    <rxjava.version>3.1.5</rxjava.version>
     <jspecify.version>1.0.0</jspecify.version>
     <slf4j.version>2.0.17</slf4j.version>
     <truth.version>1.4.4</truth.version>
@@ -65,7 +64,6 @@
     <dependency>
       <groupId>io.reactivex.rxjava3</groupId>
       <artifactId>rxjava</artifactId>
-      <version>${rxjava.version}</version>
     </dependency>
     <dependency>
       <groupId>org.jspecify</groupId>

pom.xml

@@ -65,7 +65,7 @@
     <slf4j.version>2.0.17</slf4j.version>
     <truth.version>1.4.5</truth.version>
     <jspecify.version>1.0.0</jspecify.version>
-    <rxjava.version>3.1.5</rxjava.version>
+    <rxjava.version>3.1.12</rxjava.version>
     <reactor-core.version>3.7.0</reactor-core.version>
     <wiremock.version>2.35.1</wiremock.version>
     <assertj.version>3.27.7</assertj.version>