Fix incomplete mergify rules
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

mbedmicro/mbed,mbedmicro/mbed,mbedmicro/mbed,kjbracey-arm/mbed,kjbracey-arm/mbed,mbedmicro/mbed,kjbracey-arm/mbed,mbedmicro/mbed,kjbracey-arm/mbed