[release/v2.16] fix cert-manager validating webhook

[xrstf]

What this PR does / why we need it:
When setting up the Helm chart, I accidentally copypasted the wrong path here. This can lead to errors like

Error from server (InternalError): error when creating "charts/cert-manager/test/certificate.yaml": Internal error occurred: failed calling webhook "webhook.cert-manager.io": validating webhook may not return response.patch

In the master branch, #6739 takes care of updating and fixing cert-manager.

Does this PR introduce a user-facing change?:

Fix cert-manager validating webhook

[rastislavs]

/lgtm
/approve

[kubermatic-bot]

LGTM label has been added.

Git tree hash: 1ac7f78f7c19829e57278303a8c1701e88c1c735

[kubermatic-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: rastislavs, xrstf

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:

• charts/OWNERS [rastislavs,xrstf]

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

[xrstf]

/cherrypick release/v2.15

[kubermatic-bot]

@xrstf: once the present PR merges, I will cherry-pick it on top of release/v2.15 in a new PR and assign it to you.

In response to this:

/cherrypick release/v2.15

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[kubermatic-bot]

@xrstf: new pull request created: #6742

In response to this:

/cherrypick release/v2.15

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[xrstf]

/cherrypick release/v2.14

[kubermatic-bot]

@xrstf: #6741 failed to apply on top of branch "release/v2.14":

Applying: fix cert-manager validating webhook
Using index info to reconstruct a base tree...
A	charts/cert-manager/Chart.yaml
A	charts/cert-manager/templates/webhook-validating-webhook.yaml
Falling back to patching base and 3-way merge...
Auto-merging config/cert-manager/templates/webhook-validating-webhook.yaml
Auto-merging config/cert-manager/Chart.yaml
CONFLICT (content): Merge conflict in config/cert-manager/Chart.yaml
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 fix cert-manager validating webhook
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

In response to this:

/cherrypick release/v2.14

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.