Remove migration script

Problem/Motivation

The migration script is not generic enough for a contributed module as it was created for a specific group in mind.

Proposed resolution

Remove the migration script and let potential end users migrate existing content reminders into a content_reminder table based on their specific setup.

Remove the migration script

In the file content_reminders.install replace the call to the migration script with a check to see if the content_reminder table exists. If the table does not exist, create the table, otherwise do nothing.