Remove generation for c.g.gwtexpui.* JavaDoc
Remove generation for c.g.gwtexpui.* JavaDoc

The JavaDoc for com.google.gwtexpui.* cannot be generated
because the source files are not accessible anymore.

Failing to generate the JavaDocs caused the Gerrit build to
fail with 'No source files for package com.google.gwtexpui...'.

Change-Id: Ie36e650962636813d8f9f615e495a980b7280420

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