Bump the migrator-servlet group across 1 directory with 3 updates

Bumps the migrator-servlet group with 3 updates in the /migrator/migrator-servlet directory: [com.google.appengine:appengine-api-1.0-sdk](https://github.com/GoogleCloudPlatform/appengine-java-standard), [com.google.cloud.tools:appengine-maven-plugin](https://github.com/GoogleCloudPlatform/appengine-plugins) and [org.codehaus.mojo:versions-maven-plugin](https://github.com/mojohaus/versions).


Updates `com.google.appengine:appengine-api-1.0-sdk` from 2.0.16 to 2.0.31
- [Release notes](https://github.com/GoogleCloudPlatform/appengine-java-standard/releases)
- [Commits](GoogleCloudPlatform/appengine-java-standard@v2.0.16...v2.0.31)

Updates `com.google.cloud.tools:appengine-maven-plugin` from 1.3.1 to 2.8.3
- [Release notes](https://github.com/GoogleCloudPlatform/appengine-plugins/releases)
- [Changelog](https://github.com/GoogleCloudPlatform/appengine-plugins/blob/main/CHANGELOG.md)
- [Commits](https://github.com/GoogleCloudPlatform/appengine-plugins/commits)

Updates `org.codehaus.mojo:versions-maven-plugin` from 2.16.0 to 2.18.0
- [Release notes](https://github.com/mojohaus/versions/releases)
- [Changelog](https://github.com/mojohaus/versions/blob/master/ReleaseNotes.md)
- [Commits](mojohaus/versions@2.16.0...2.18.0)

---
updated-dependencies:
- dependency-name: com.google.appengine:appengine-api-1.0-sdk
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: migrator-servlet
- dependency-name: com.google.cloud.tools:appengine-maven-plugin
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: migrator-servlet
- dependency-name: org.codehaus.mojo:versions-maven-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: migrator-servlet
...

Signed-off-by: dependabot[bot] <[email protected]>

migrator/migrator-servlet/pom.xml

@@ -25,7 +25,7 @@
     <dependency>
       <groupId>com.google.appengine</groupId>
       <artifactId>appengine-api-1.0-sdk</artifactId>
-      <version>2.0.16</version>
+      <version>2.0.31</version>
     </dependency>
     <dependency>
       <groupId>javax.servlet</groupId>
@@ -64,15 +64,15 @@
       <plugin>
         <groupId>com.google.cloud.tools</groupId>
         <artifactId>appengine-maven-plugin</artifactId>
-        <version>1.3.1</version>
+        <version>2.8.3</version>
         <configuration>
         </configuration>
       </plugin>
 
       <plugin>
         <groupId>org.codehaus.mojo</groupId>
         <artifactId>versions-maven-plugin</artifactId>
-        <version>2.16.0</version>
+        <version>2.18.0</version>
         <executions>
           <execution>
             <phase>compile</phase>