chore: Add JSpecify to BigTable and BQStorage modules

Author: lqiu96

java-bigquerystorage/google-cloud-bigquerystorage/pom.xml

@@ -177,6 +177,10 @@
       <groupId>org.apache.arrow</groupId>
       <artifactId>arrow-vector</artifactId>
     </dependency>
+    <dependency>
+      <groupId>org.jspecify</groupId>
+      <artifactId>jspecify</artifactId>
+    </dependency>
 
     <dependency>
       <groupId>io.opentelemetry</groupId>

java-bigtable/google-cloud-bigtable/pom.xml

@@ -221,6 +221,10 @@
       <groupId>org.threeten</groupId>
       <artifactId>threetenbp</artifactId>
     </dependency>
+    <dependency>
+      <groupId>org.jspecify</groupId>
+      <artifactId>jspecify</artifactId>
+    </dependency>
 
     <!-- metrics dependencies -->
     <dependency>