JSON.load_file: explictly load the file as UTF-8 #652

# to view logs

Job	Run time
Ruby memcheck	53s
ruby-versions / Generate Ruby versions	3s
ubuntu-22.04 2.7	57s
ubuntu-22.04 3.0	29s
ubuntu-22.04 3.1	31s
ubuntu-22.04 3.2	30s
ubuntu-22.04 3.3	34s
ubuntu-22.04 head	1m 20s
ubuntu-22.04 jruby	1m 9s
ubuntu-22.04 jruby-head	1m 8s
macos-13 2.7	2m 5s
macos-13 3.0	39s
macos-13 3.1	37s
macos-13 3.2	39s
macos-13 3.3	38s
macos-13 head	35s
macos-13 jruby	1m 39s
macos-13 jruby-head	1m 37s
macos-14 2.7	51s
macos-14 3.0	23s
macos-14 3.1	44s
macos-14 3.2	21s
macos-14 3.3	23s
macos-14 head	22s
macos-14 jruby	51s
macos-14 jruby-head	42s
windows-latest 2.7	5m 1s
windows-latest 3.0	2m 47s
windows-latest 3.1	2m 39s
windows-latest 3.2	3m 21s
windows-latest 3.3	3m 46s
windows-latest head	1m 27s
windows-latest mswin	1m 9s
ubuntu-latest jruby-9.4	1m 9s
macos-latest truffleruby-head	49s
ubuntu-latest truffleruby-head	1m 56s
	44m 44s

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