chore(datastore): use local version in snippets to fix build

Author: lqiu96

java-datastore/samples/snippets/pom.xml

@@ -41,6 +41,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-datastore</artifactId>
+      <version>2.40.0</version>
     </dependency>
     <!-- [END datastore_install_with_bom] -->