Fix t() calls in FencesPresetForm

Problem/Motivation

FILE: /var/www/html/web/modules/custom/fences/modules/fences_presets/src/Form/FencesPresetForm.php
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FOUND 0 ERRORS AND 4 WARNINGS AFFECTING 4 LINES
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 112 | WARNING | t() calls should be avoided in classes, use \Drupal\Core\StringTranslation\StringTranslationTrait and $this->t() instead
 127 | WARNING | t() calls should be avoided in classes, use \Drupal\Core\StringTranslation\StringTranslationTrait and $this->t() instead
 142 | WARNING | t() calls should be avoided in classes, use \Drupal\Core\StringTranslation\StringTranslationTrait and $this->t() instead
 157 | WARNING | t() calls should be avoided in classes, use \Drupal\Core\StringTranslation\StringTranslationTrait and $this->t() instead
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Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes