ci: do not let Mergify remove the ok-to-test label

Sometimes Mergify removed the `ok-to-test` label before the Pull Request
Commentor action have been run. With the updated commentor action, the
`ok-to-test` label is removed after leaving comments. There is no need
for Mergify to remove the label anymore.

Signed-off-by: Niels de Vos <ndevos@redhat.com>

.mergify.yml

@@ -73,9 +73,6 @@ pull_request_rules:
         message: "This pull request now has conflicts with the target branch.
         Could you please resolve conflicts and force push the corrected
         changes? 🙏"
-      label:
-        remove:
-          - ok-to-test
 
   - name: update dependencies by dependabot (skip commitlint)
     conditions:
@@ -108,9 +105,6 @@ pull_request_rules:
       queue:
         name: default
       delete_head_branch: {}
-      label:
-        remove:
-          - ok-to-test
 
   - name: dismiss review of merged pull request
     conditions:
@@ -118,9 +112,6 @@ pull_request_rules:
       - merged
     actions:
       dismiss_reviews: {}
-      label:
-        remove:
-          - ok-to-test
 
   - name: automatic merge
     conditions:
@@ -153,9 +144,6 @@ pull_request_rules:
       queue:
         name: default
       delete_head_branch: {}
-      label:
-        remove:
-          - ok-to-test
 
   - name: automatic merge PR having ready-to-merge label
     conditions:
@@ -187,9 +175,6 @@ pull_request_rules:
       queue:
         name: default
       delete_head_branch: {}
-      label:
-        remove:
-          - ok-to-test
 
   - name: backport patches to release-v3.6 branch
     conditions:
@@ -247,9 +232,6 @@ pull_request_rules:
       queue:
         name: default
       delete_head_branch: {}
-      label:
-        remove:
-          - ok-to-test
 
   ##
   ## Automatically set/remove labels