Mark any_instance proxy methods as private if they were private #890

Job	Run time
Rubocop	27s
Ruby 3.3	2m 50s
Ruby 2.7 (Windows)	3m 35s
Ruby 3.2	2m 47s
Legacy Ruby Builds (2.1.9)	1m 9s
Ruby 2.6 (Windows)	3m 46s
Ruby 3.1	2m 41s
Legacy Ruby Builds (2.0)	1m 6s
Ruby 2.5 (Windows)	2m 11s
Ruby 3.0	2m 38s
Legacy Ruby Builds (1.9.3)	1m 20s
Ruby 2.4 (Windows)	2m 17s
Ruby 2.7	3m 2s
Legacy Ruby Builds (1.9.2)	1m 59s
Ruby 2.3 (Windows)	2m 11s
Ruby 2.6	2m 49s
Legacy Ruby Builds (1.8.7)	1m 13s
Ruby 2.2 (Windows)	2m 18s
Ruby 2.5	2m 34s
Legacy Ruby Builds (REE)	1m 22s
Ruby 2.4	2m 26s
Legacy Ruby Builds (JRuby 1.7)	3m 30s
Ruby 2.3	2m 32s
Legacy Ruby Builds (JRuby 1.7 1.8 mode)	3m 5s
Ruby 2.2	3m 1s
Legacy Ruby Builds (JRuby 9.1.17.0)	4m 11s
Ruby ruby-head	1m 8s
Ruby jruby-9.2.13.0	6m 20s
Ruby 2.7 with diff-lcs 1.3	2m 53s
Ruby 2.7 with diff-lcs 1.4.3	2m 51s
	1h 16m 12s

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