test-requires: Update to use the latest Pylint
test-requires: Update to use the latest Pylint

Current specified Pylint(==0.25.0) are not enough to support Python 3.
This patch updates test-requires to use the latest one.

Signed-off-by: IWASE Yusuke <bb80e84cc9f5a8f01385872ee89032beb5d4eba7@gmail.com>
Signed-off-by: FUJITA Tomonori <93dac1fe9c4b2a3957982200319981492ad4976e@lab.ntt.co.jp>

fujita/ryu,gareging/SDN_Framework,lagopus/ryu-lagopus-ext,shinpeimuraoka/ryu,iwaseyusuke/ryu,fujita/ryu,gareging/SDN_Framework,fujita/ryu,gareging/SDN_Framework,pichuang/ryu,pichuang/ryu,zangree/ryu,fkakuma/ryu,lagopus/ryu-lagopus-ext,osrg/ryu,lagopus/ryu-lagopus-ext,iwaseyusuke/ryu,shinpeimuraoka/ryu,fujita/ryu,shinpeimuraoka/ryu,osrg/ryu,hisaharu/ryu,fkakuma/ryu,iwaseyusuke/ryu,hisaharu/ryu,TakeshiTseng/ryu,TakeshiTseng/ryu,shinpeimuraoka/ryu,pichuang/ryu,hisaharu/ryu,fkakuma/ryu,TakeshiTseng/ryu,osrg/ryu,fujita/ryu,fkakuma/ryu,zangree/ryu,gareging/SDN_Framework,lagopus/ryu-lagopus-ext,hisaharu/ryu,shinpeimuraoka/ryu,lagopus/ryu-lagopus-ext,fkakuma/ryu,zangree/ryu,TakeshiTseng/ryu,zangree/ryu,osrg/ryu,osrg/ryu,pichuang/ryu,TakeshiTseng/ryu,zangree/ryu,iwaseyusuke/ryu,pichuang/ryu,hisaharu/ryu,gareging/SDN_Framework,iwaseyusuke/ryu