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Remove YEAR field of all generated files and fix kubernetes boilerplate checker

**What this PR does / why we need it**:
Remove YEAR field of all generated files and fix kubernetes boilerplate checker
xref: [remove YEAR fileds in gengo #91](https://github.com/kubernetes/gengo/pull/91)

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes [#gengo/issues/24](https://github.com/kubernetes/gengo/issues/24)

**Special notes for your reviewer**:
/cc @thockin @lavalamp @sttts 

**Release note**:

```release-note
NONE
```