php: ran php-cs-fixer again

src/php/tests/bootstrap.php

...hp/tests/generated_code/GeneratedCodeWithCallbackTest.php

src/php/tests/generated_code/math_client.php

src/php/tests/unit_tests/CallCredentials3Test.php

src/php/tests/unit_tests/CallTest.php

src/php/tests/unit_tests/ChannelCredentialsTest.php

src/php/tests/unit_tests/ChannelTest.php

src/php/tests/unit_tests/EndToEndTest.php

src/php/tests/unit_tests/ServerTest.php

src/php/tests/unit_tests/TimevalTest.php