gwt.xml change from internal change.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=260785140

Author: dimo414

guava-gwt/test/com/google/common/collect/testModule.gwt.xml

@@ -11,7 +11,6 @@
   <inherits name="com.google.common.io.Io"/>
   <inherits name="com.google.common.testing.Testing"/>
   <inherits name="com.google.common.truth.Truth"/>
-  <inherits name="com.google.common.truth.Truth8"/>
   <entry-point class="com.google.common.collect.TestModuleEntryPoint"/>
 
   <source path=""/>