Fix must-gather repo location

[razo7]

The must-gather repo on quay is node-maintenance-must-gather and not node-maintenance-opreator-must-gather. This problem led to calling must-gather-push target and failing to push the new image to quay.

docker push quay.io/medik8s/node-maintenance-operator-must-gather:latest
The push refers to repository [quay.io/medik8s/nod
.
.
.
unauthorized: access to the requested resource is not authorized
make: *** [Makefile:255: must-gather-push] Error 1

The problem was introduced in #112 PR

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: clobrano, razo7

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [clobrano,razo7]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[razo7]

/retest