Merge pull request #5269 from stanley-cheung/fix-php-copyright

src/php/ext/grpc/call.c

src/php/ext/grpc/channel.c

src/php/tests/generated_code/AbstractGeneratedCodeTest.php

src/php/tests/unit_tests/CallCredentials2Test.php

src/php/tests/unit_tests/CallCredentials3Test.php

src/php/tests/unit_tests/CallCredentialsTest.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