Remove back pointer from Real to VALUE #437

Job	Run time
ruby-versions / Generate Ruby versions	2s
ubuntu-latest 2.7	1m 7s
ubuntu-latest 3.0	34s
ubuntu-latest 3.1	39s
ubuntu-latest 3.2	39s
ubuntu-latest 3.3	40s
ubuntu-latest 3.4	36s
ubuntu-latest debug	46s
ubuntu-latest head	33s
macos-latest 2.7	56s
macos-latest 3.0	25s
macos-latest 3.1	35s
macos-latest 3.2	23s
macos-latest 3.3	22s
macos-latest 3.4	21s
macos-latest debug	29s
macos-latest head	22s
macos-14 2.7	57s
macos-14 3.0	23s
macos-14 3.1	29s
macos-14 3.2	24s
macos-14 3.3	19s
macos-14 3.4	23s
macos-14 debug	27s
macos-14 head	22s
windows-latest 2.7	5m 11s
windows-latest 3.3	3m 18s
windows-latest 3.4	4m 10s
windows-latest head	3m 35s
windows-latest mingw	3m 38s
windows-latest mswin	2m 43s
	35m 48s

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