Remove back pointer from Real to VALUE #492

Job	Run time
ruby-versions / Generate Ruby versions	2s
ubuntu-latest 2.5	52s
ubuntu-latest 2.6	1m 0s
ubuntu-latest 2.7	1m 5s
ubuntu-latest 3.0	35s
ubuntu-latest 3.1	38s
ubuntu-latest 3.2	40s
ubuntu-latest 3.3	37s
ubuntu-latest 3.4	36s
ubuntu-latest debug	35s
ubuntu-latest head	37s
ubuntu-latest truffleruby	1m 34s
ubuntu-latest truffleruby-head	1m 31s
macos-latest 2.6	55s
macos-latest 2.7	58s
macos-latest 3.0	26s
macos-latest 3.1	31s
macos-latest 3.2	25s
macos-latest 3.3	23s
macos-latest 3.4	19s
macos-latest debug	23s
macos-latest head	20s
macos-latest truffleruby	53s
macos-latest truffleruby-head	57s
macos-14 2.6	35s
macos-14 2.7	36s
macos-14 3.0	27s
macos-14 3.1	27s
macos-14 3.2	18s
macos-14 3.3	19s
macos-14 3.4	21s
macos-14 debug	21s
macos-14 head	20s
macos-14 truffleruby	55s
macos-14 truffleruby-head	52s
windows-latest 2.5	3m 17s
windows-latest 2.6	3m 44s
windows-latest 2.7	4m 5s
windows-latest 3.0	2m 58s
windows-latest 3.1	2m 48s
windows-latest 3.2	2m 41s
windows-latest 3.3	2m 51s
windows-latest 3.4	3m 15s
windows-latest head	2m 52s
windows-latest mingw	3m 11s
windows-latest mswin	2m 39s
	56m 44s

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