[ci] Delete lock.yml (#4251)

.github/lock.yml

-# Configuration for Lock Threads - https://github.com/dessant/lock-threads-app
-
-# Number of days of inactivity before a closed issue or pull request is locked
-daysUntilLock: 60
-
-# Skip issues and pull requests created before a given timestamp. Timestamp must
-# follow ISO 8601 (`YYYY-MM-DD`). Set to `false` to disable
-skipCreatedBefore: false
-
-# Issues and pull requests with these labels will be ignored. Set to `[]` to disable
-exemptLabels: ['effectiveness', 'efficiency', 'feature request', 'help wanted']
-
-# Label to add before locking, such as `outdated`. Set to `false` to disable
-lockLabel: false
-
-# Comment to post before locking. Set to `false` to disable
-lockComment: false
-
-# Assign `resolved` as the reason for locking. Set to `false` to disable
-setLockReason: true
-
-# Limit to only `issues` or `pulls`
-# only: issues
-
-# Optionally, specify configuration settings just for `issues` or `pulls`
-# issues:
-#   exemptLabels:
-#     - help-wanted
-#   lockLabel: outdated
-
-# pulls:
-#   daysUntilLock: 30
-
-# Repository to extend settings from
-# _extends: repo