Automatic merge from submit-queue

Remove old node role label that is not used by kubeadm

**What this PR does / why we need it**:
This label hasn't been used by kubeadm since v1.5.
v1.5 support was dropped when v1.6 arrived due to a potential security flaw and the earlier alpha status.
So this label hasn't been used for around three months.
It makes sense to remove it in time for v1.8, could already have been done for v1.7

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```
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