fix testing-tool example link (#488)
fix testing-tool example link (#488)


camelburrito/amp-by-example,ampproject/amp-by-example,ampproject/amp-by-example,ampproject/amp-by-example,ampproject/amp-by-example,camelburrito/amp-by-example,camelburrito/amp-by-example,camelburrito/amp-by-example