Correct location for CoC

[arun-gupta]

Move the CoC from https://github.com/opea-project/GenAIExamples/blob/main/CODE_OF_CONDUCT.md to https://github.com/opea-project/Governance as this is widely applicable to the entire project.

[preethivenkatesh]

@arun-gupta Does the change seem reasonable?

[chensuyue]

As the PR shows we have unify those docs into opea-project/docs#21, I will close this issue. Feel free to re-open if you have new comments.