test

Fix reference error of @@accept_charset class variable. #221

Job	Run time
ruby-versions / Generate Ruby versions	3s
build (2.5 / ubuntu-latest)	21s
build (2.5 / windows-latest)	3m 51s
build (2.6 / ubuntu-latest)	22s
build (2.6 / macos-latest)	36s
build (2.6 / windows-latest)	3m 2s
build (2.7 / ubuntu-latest)	31s
build (2.7 / macos-latest)	27s
build (2.7 / windows-latest)	2m 0s
build (3.0 / ubuntu-latest)	11s
build (3.0 / macos-latest)	17s
build (3.0 / windows-latest)	1m 49s
build (3.1 / ubuntu-latest)	9s
build (3.1 / macos-latest)	12s
build (3.1 / windows-latest)	1m 24s
build (3.2 / ubuntu-latest)	17s
build (3.2 / macos-latest)	11s
build (3.2 / windows-latest)	1m 2s
build (3.3 / ubuntu-latest)	11s
build (3.3 / macos-latest)	10s
build (3.3 / windows-latest)	1m 26s
build (3.4 / ubuntu-latest)	9s
build (3.4 / macos-latest)	12s
build (3.4 / windows-latest)	2m 42s
build (head / ubuntu-latest)	12s
build (head / macos-latest)	10s
build (jruby / ubuntu-latest)	36s
build (jruby-head / ubuntu-latest)	48s
build (truffleruby / ubuntu-latest)	23s
build (truffleruby / macos-latest)	17s
build (truffleruby-head / ubuntu-latest)	28s
build (truffleruby-head / macos-latest)	19s
build (mingw / windows-latest)	55s
build (mswin / windows-latest)	2m 24s
	28m 7s

Provide feedback