docs: update DeepModeling email address (#5062)

Update the DeepModeling email from contact@deepmodeling.org to
deepmodeling@deepmodeling.com.
The former is no longer used.

Generated by the task: njzjz-bot/njzjz-bot#17.


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## Summary by CodeRabbit

* **Documentation**
  * Updated contact email address in contributing guidelines.

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Author: njzjz-bot

CONTRIBUTING.md

@@ -145,4 +145,4 @@ Now, your PR is successfully submitted! After this PR is merged, you will automa
 
 ## Contact us
 
-E-mail: contact@deepmodeling.org
+E-mail: deepmodeling@deepmodeling.com