docs(readme): remove broken tags

README.md

@@ -3,7 +3,6 @@
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 [![codecov](https://codecov.io/gh/watson-developer-cloud/node-sdk/branch/master/graph/badge.svg)](https://codecov.io/gh/watson-developer-cloud/node-sdk)
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 [![npm-version](https://img.shields.io/npm/v/ibm-watson.svg)](https://www.npmjs.com/package/ibm-watson)
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