Updated stackoverflow tag (#8217)

.github/ISSUE_TEMPLATE/40-research-documentation-issue.md

@@ -9,7 +9,7 @@ Please make sure that this is a documentation issue.
 
 As per our GitHub Policy (https://github.com/tensorflow/models/blob/master/ISSUES.md), we only address code bugs, documentation issues, and feature requests on GitHub.
 
-Please go to Stack Overflow (http://stackoverflow.com/questions/tagged/tensorflow) for help and support.
+Please go to Stack Overflow (http://stackoverflow.com/questions/tagged/tensorflow-model-garden) for help and support.
 
 The research models (https://github.com/tensorflow/models/tree/master/research) are a large collection of models implemented in TensorFlow by researchers. They are not officially supported. It is up to the individual researchers to maintain the models and/or provide support on issues and pull requests.
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