Change encode EUC-JP to UTF-8 #98

Job	Run time
ruby-versions / Generate Ruby versions	4s
test (2.5, ubuntu-latest)	28s
test (2.5, windows-latest)	3m 59s
test (2.6, ubuntu-latest)	27s
test (2.6, macos-latest)	33s
test (2.6, windows-latest)	2m 29s
test (2.7, ubuntu-latest)	30s
test (2.7, macos-latest)	31s
test (2.7, windows-latest)	2m 53s
test (3.0, ubuntu-latest)	15s
test (3.0, macos-latest)	16s
test (3.0, windows-latest)	1m 48s
test (3.1, ubuntu-latest)	18s
test (3.1, macos-latest)	19s
test (3.1, windows-latest)	1m 49s
test (3.2, ubuntu-latest)	15s
test (3.2, macos-latest)	17s
test (3.2, windows-latest)	1m 34s
test (3.3, ubuntu-latest)	16s
test (3.3, macos-latest)	19s
test (3.3, windows-latest)	1m 38s
test (head, ubuntu-latest)	20s
test (head, macos-latest)	22s
test (head, windows-latest)	1m 4s
test (jruby, ubuntu-latest)	4m 32s
test (jruby-head, ubuntu-latest)	4m 21s
test (truffleruby, ubuntu-latest)	1m 37s
test (truffleruby-head, ubuntu-latest)	1m 54s
	35m 8s

Provide feedback