Remove back pointer from Real to VALUE #545

Job	Run time
ruby-versions / Generate Ruby versions	6s
ubuntu-latest 2.5	58s
ubuntu-latest debug	34s
ubuntu-latest 2.6	1m 4s
ubuntu-latest 2.7	1m 4s
ubuntu-latest head	45s
ubuntu-latest truffleruby	1m 33s
ubuntu-latest 3.0	36s
macos-latest 2.7	54s
macos-latest 2.6	1m 0s
macos-latest 3.0	32s
macos-latest 3.1	34s
ubuntu-latest 3.3	43s
macos-latest head	24s
ubuntu-latest 3.2	44s
macos-latest 3.2	33s
macos-latest 3.3	22s
macos-14 2.6	44s
ubuntu-latest truffleruby-head	1m 39s
ubuntu-latest 3.4	36s
macos-14 3.1	46s
macos-14 3.0	30s
macos-latest truffleruby-head	1m 0s
macos-14 3.4	33s
windows-latest 2.7	3m 42s
macos-14 debug	30s
ubuntu-latest 3.1	36s
windows-latest 3.0	2m 29s
macos-14 head	28s
macos-latest truffleruby	52s
macos-14 2.7	43s
windows-latest head	2m 1s
macos-latest 3.4	26s
windows-latest 3.4	1m 58s
macos-14 3.2	32s
windows-latest 2.5	2m 9s
windows-latest 2.6	3m 2s
windows-latest mingw	1m 52s
macos-14 truffleruby-head	1m 5s
windows-latest 3.2	2m 15s
windows-latest 3.3	2m 21s
windows-latest 3.1	2m 21s
macos-latest debug	29s
macos-14 3.3	22s
macos-14 truffleruby	52s
windows-latest mswin	1m 15s
	50m 34s

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