Fixes file upload test on Selenium 3

[aik099]

Fixes this error from the https://github.com/minkphp/MinkSelenium2Driver/pull/383:

2) Behat\Mink\Tests\Driver\Js\ChangeEventTest::testSetValueChangeEvent with data set "file" ('the-file', '/home/runner/work/MinkSeleniu...e1.txt', '/home/runner/work/MinkSeleniu...e2.txt')
WebDriver\Exception\InvalidArgument: File not found: /home/runner/work/MinkSelenium2Driver/MinkSelenium2Driver/vendor/mink/driver-testsuite/web-fixtures/file1.txt
Build info: version: '3.141.59', revision: 'e82be7d358', time: '2018-11-14T08:25:53'
System info: host: 'fv-az697-197', ip: '10.1.0.44', os.name: 'Linux', os.arch: 'amd64', os.version: '5.15.0-1056-azure', java.version: '1.8.0_292'
Driver info: driver.version: unknown

Inspired by the @uuf6429 work on the https://github.com/minkphp/webdriver-classic-driver project.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 87.42%. Comparing base (4ca4083) to head (d6fb204).

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #385      +/-   ##
============================================
- Coverage     90.19%   87.42%   -2.78%     
  Complexity      168      168              
============================================
  Files             1        1              
  Lines           469      469              
============================================
- Hits            423      410      -13     
- Misses           46       59      +13     

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[aik099]

Keep in mind this might conflict with #383. Looks good otherwise.

Thank you for the warning. We will see if GitHub is clever enough to perform interactive conflict resolution upon merge.