Fix attribute names in phpunit configurations

[vishwarajanand]

There are no name defined in PHPunit configuration files which throws unnecessary warnings while working with PHPUnit. This is very confusing and can be removed easily.

Ex:

➜  Firestore git:(feat_fs_bulkwriter1) ✗ XDEBUG_MODE=coverage  vendor/bin/phpunit --verbose -c phpunit.xml.dist tests/Unit/RateLimiterTest.php                                              
PHPUnit 8.5.27 #StandWithUkraine

Runtime:       PHP 8.1.5 with Xdebug 3.1.2
Configuration: /usr/local/google/home/vishwarajanand/github/google-cloud-php/Firestore/phpunit.xml.dist

  Warning - The configuration file did not pass validation!
  The following problems have been detected:

  Line 4:
  - Element 'testsuite': The attribute 'name' is required but missing.

  Test results may not be as expected.


...                                                                 3 / 3 (100%)

Time: 37 ms, Memory: 4.00 MB

OK (3 tests, 33 assertions)
➜  Firestore git:(feat_fs_bulkwriter1) ✗

vs

➜  Firestore git:(feat_fs_bulkwriter1) ✗ XDEBUG_MODE=coverage  vendor/bin/phpunit --verbose -c phpunit.xml.dist tests/Unit/RateLimiterTest.php
PHPUnit 8.5.27 #StandWithUkraine

Runtime:       PHP 8.1.5 with Xdebug 3.1.2
Configuration: /usr/local/google/home/vishwarajanand/github/google-cloud-php/Firestore/phpunit.xml.dist

...                                                                 3 / 3 (100%)

Time: 39 ms, Memory: 4.00 MB

OK (3 tests, 33 assertions)
➜  Firestore git:(feat_fs_bulkwriter1) ✗

All the "unnecessary" warnings are gone once we add name="Unit Tests" in php unit config files.