deps: update dependency com.google.cloud:google-cloud-core to v2.8.18 (#1027)

Author: renovate-bot

java-dialogflow/samples/install-without-bom/pom.xml

@@ -36,7 +36,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-core</artifactId>
-      <version>2.8.16</version>
+      <version>2.8.18</version>
       <scope>test</scope>
       <classifier>tests</classifier>
     </dependency>

java-dialogflow/samples/snapshot/pom.xml

@@ -34,7 +34,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-core</artifactId>
-      <version>2.8.16</version>
+      <version>2.8.18</version>
       <scope>test</scope>
       <classifier>tests</classifier>
     </dependency>

java-dialogflow/samples/snippets/pom.xml

@@ -47,7 +47,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-core</artifactId>
-      <version>2.8.16</version>
+      <version>2.8.18</version>
       <scope>test</scope>
       <classifier>tests</classifier>
     </dependency>