test(deps): update dependency junit:junit to v4 (#252)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [junit:junit](http://junit.org) ([source](https://togithub.com/junit-team/junit4)) | major | `0.21.3-SNAPSHOT` -> `4.13.1` |

---

### Renovate configuration

:date: **Schedule**: At any time (no schedule defined).

:vertical_traffic_light: **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

:recycle: **Rebasing**: Renovate will not automatically rebase this PR, because other commits have been found.

:no_bell: **Ignore**: Close this PR and you won't be reminded about this update again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

---

This PR has been generated by [WhiteSource Renovate](https://renovate.whitesourcesoftware.com). View repository job log [here](https://app.renovatebot.com/dashboard#github/googleapis/java-game-servers).

samples/install-without-bom/pom.xml

@@ -23,25 +23,24 @@
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
   </properties>
 
-  <!-- {x-version-update-start:google-cloud-game-servers:released} -->
   <dependencies>
     <!-- [START game_servers_install_without_bom] -->
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-game-servers</artifactId>
-      <version>0.21.3-SNAPSHOT</version>
+      <version>0.21.2</version>
     </dependency>
     <!-- [END game_servers_install_without_bom] -->
     <dependency>
       <groupId>com.google.code.gson</groupId>
       <artifactId>gson</artifactId>
-      <version>0.21.3-SNAPSHOT</version>
+      <version>2.8.6</version>
     </dependency>
 
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
-      <version>0.21.3-SNAPSHOT</version>
+      <version>4.13.1</version>
       <scope>test</scope>
     </dependency>
     <dependency>
@@ -51,7 +50,6 @@
       <scope>test</scope>
     </dependency>
   </dependencies>
-  <!-- {x-version-update-end} -->
 
   <!-- compile and run all snippet tests -->
   <build>

samples/snippets/pom.xml

@@ -37,13 +37,11 @@
 
   <dependencies>
     <!-- TODO: use libraries-bom when google-cloud-game-servers is included -->
-    <!-- [START game_servers_install_with_bom] -->
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-game-servers</artifactId>
       <version>0.21.1</version>
     </dependency>
-    <!-- [END game_servers_install_with_bom] -->
     <dependency>
       <groupId>com.google.code.gson</groupId>
       <artifactId>gson</artifactId>