Fix incomplete mergify rules

1. If a PR is closed but not merged then remove all labels
2. If a release version is added and there are release version missing
   or Release review required, then remove those labels

3. In the check for conflicts rule, add the condition 'open' so
   that it isn't applied to closed or merged PRs

.mergify.yml

@@ -102,6 +102,7 @@ pull_request_rules:
   # Conflict in the PR - needs: work and a comment to notify a user
   - name: "label needs: work when there is a conflict"
     conditions:
+      - open
       - conflict
     actions:
       label:
@@ -158,7 +159,7 @@ pull_request_rules:
         add: ['do not merge']
 
   # Check if version label is applied
-  - name: release version is a must for merged PRs
+  - name: release version is a must for merged PRs part 1
     conditions:
       - merged
       - -label~=^(release-version)
@@ -169,4 +170,22 @@ pull_request_rules:
       comment:
         message: This PR does not contain release version label after merging.
 
+  # If there is a release version remove 'release version missing' and / or 
+  # release review required
+  - name: release version is a must for merged PRs part 2
+    conditions:
+      - merged
+      - -label=^(release-version)
+    actions:
+      label:
+        remove: ['release version missing', 'Release review required']                
+        
+ # Clean-up if closed but not merged
+  - name: remove release version and needs labels
+    conditions:
+      - closed
+      - -merged
+    actions:
+      label:
+        remove_all=True