Remove some unused variables

Remove some unused variables

phpcs correctly found these

Eileens-MacBook-Pro:civicrm eileenmcnaughton$ phpcs --standard=DrupalPractice CRM/ACL

FILE: /Users/eileenmcnaughton/buildkit/build/dmaster/sites/all/modules/civicrm/CRM/ACL/Form/WordPress/Permissions.php
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FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
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 197 | WARNING | Unused global variable .
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FILE: /Users/eileenmcnaughton/buildkit/build/dmaster/sites/all/modules/civicrm/CRM/ACL/Form/ACL.php
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FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
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 97 | WARNING | Unused variable .
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FILE: /Users/eileenmcnaughton/buildkit/build/dmaster/sites/all/modules/civicrm/CRM/ACL/BAO/ACL.php
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FOUND 0 ERRORS AND 3 WARNINGS AFFECTING 3 LINES
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 171 | WARNING | Unused variable .
 172 | WARNING | Unused variable .
 296 | WARNING | Unused variable .
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