Fix Drupal Coding Standard Errors

Problem/Motivation

$ phpcs --standard=Drupal .

FILE: /faker_generate/src/Form/FakerGenerateContentForm.php
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FOUND 1 ERROR AFFECTING 1 LINE
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 123 | ERROR | [x] Namespaced classes/interfaces/traits should be referenced with use statements
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FILE: /faker_generate/src/FakerGenerate.php
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FOUND 6 ERRORS AFFECTING 2 LINES
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  93 | ERROR | [x] TRUE, FALSE and NULL must be uppercase; expected "NULL" but found "null"
  93 | ERROR | [x] Expected one space after the comma, 0 found
  93 | ERROR | [x] Expected one space after the comma, 0 found
 101 | ERROR | [x] TRUE, FALSE and NULL must be uppercase; expected "NULL" but found "null"
 101 | ERROR | [x] Expected one space after the comma, 0 found
 101 | ERROR | [x] Expected one space after the comma, 0 found
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Proposed resolution

Fix the errors as per Drupal coding standards.

User interface changes

NONE

API changes

NONE

Data model changes

NONE