Call to deprecated function db_drop_field(). Deprecated in drupal:8.0.0 and is removed from drupal:9.0.0. Instead, get a database connection injected into your service from the container, get its schema driver, and call dropField() on it. For example,

Total occurrences Projects affected Topmost group Category
5 4 10000 Not covered by rector
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testswarm 1.x-dev 10000 2
nodeorder 1.x-dev 10000 1
smart_ip_ban 1.x-dev 10000 1
icon 1.x-dev 10000 1