Improve history test's encoding setting #4037

Job	Run time
Debug compatibility test	5m 40s
lint	9s
ruby-versions / Generate Ruby versions	3s
rake test 2.7 (latest reline)	1m 30s
rake test 2.7	1m 26s
rake test 3.0 (latest reline)	1m 22s
rake test 3.0	1m 21s
vterm-yamatanooroti 2.7 (latest reline)	40s
rake test 3.1 (latest reline)	1m 32s
vterm-yamatanooroti 2.7	45s
rake test 3.1	1m 25s
vterm-yamatanooroti 3.0 (latest reline)	30s
rake test 3.2 (latest reline)	1m 31s
vterm-yamatanooroti 3.0	32s
rake test 3.2	1m 24s
vterm-yamatanooroti 3.1 (latest reline)	32s
rake test 3.3 (latest reline)	1m 19s
vterm-yamatanooroti 3.1	30s
rake test 3.3	1m 24s
vterm-yamatanooroti 3.2 (latest reline)	31s
rake test head (latest reline)	1m 52s
vterm-yamatanooroti 3.2	28s
rake test head	1m 52s
vterm-yamatanooroti 3.3 (latest reline)	29s
rake test truffleruby-head (latest reline)	2m 44s
vterm-yamatanooroti 3.3	34s
rake test truffleruby-head	2m 40s
vterm-yamatanooroti head (latest reline)	30s
vterm-yamatanooroti head	30s
	35m 45s

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