deps: update dependency com.google.cloud:google-cloud-core to v2.8.18 (#850)

Author: renovate-bot

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

@@ -48,7 +48,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-core</artifactId>
-      <version>2.8.17</version>
+      <version>2.8.18</version>
       <classifier>tests</classifier>
     </dependency>
   </dependencies>

java-accessapproval/samples/snapshot/pom.xml

@@ -46,7 +46,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-core</artifactId>
-      <version>2.8.17</version>
+      <version>2.8.18</version>
       <classifier>tests</classifier>
     </dependency>
   </dependencies>

java-accessapproval/samples/snippets/pom.xml

@@ -59,7 +59,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-core</artifactId>
-      <version>2.8.17</version>
+      <version>2.8.18</version>
       <classifier>tests</classifier>
     </dependency>
   </dependencies>