Migrate from legacy com.google.gwt to org.gwtproject.

org.gwtproject starts being available at the 2.10.0 release, so upgrade to that where necessary.

See google/auto#1342 (comment)

RELNOTES=n/a
PiperOrigin-RevId: 457020479

Author: cpovirk

guava-gwt/pom.xml

@@ -17,7 +17,7 @@
     This project includes GWT-friendly sources.
   </description>
   <properties>
-    <gwt.version>2.9.0</gwt.version>
+    <gwt.version>2.10.0</gwt.version>
     <gwt.plugin.version>2.8.2</gwt.plugin.version>
     <gwt.logLevel>WARN</gwt.logLevel>
   </properties>
@@ -78,13 +78,13 @@
       <scope>test</scope>
     </dependency>
     <dependency>
-      <groupId>com.google.gwt</groupId>
+      <groupId>org.gwtproject</groupId>
       <artifactId>gwt-dev</artifactId>
       <version>${gwt.version}</version>
       <scope>provided</scope>
     </dependency>
     <dependency>
-      <groupId>com.google.gwt</groupId>
+      <groupId>org.gwtproject</groupId>
       <artifactId>gwt-user</artifactId>
       <version>${gwt.version}</version>
       <scope>test</scope>
@@ -315,6 +315,7 @@
           </execution>
         </executions>
       </plugin>
+      <!-- TODO(cpovirk): We really should try tbroyer's plugin instead of this legacy one. -->
       <plugin>
         <groupId>org.codehaus.mojo</groupId>
         <artifactId>gwt-maven-plugin</artifactId>