CLN : Remove utf-8 coding cookies in source files

CLN : Remove utf-8 coding cookies in source files

On Python 3, utf-8 is the default python source code encoding. so, the
coding cookies on files that specify utf-8 are not needed anymore.

	modified:   tornado/_locale_data.py
	modified:   tornado/locale.py
	modified:   tornado/test/curl_httpclient_test.py
	modified:   tornado/test/httpclient_test.py
	modified:   tornado/test/httputil_test.py
	modified:   tornado/test/options_test.py
	modified:   tornado/test/util_test.py