Remove unused rust_object_field helpers from Jvm #684

Job	Run time
rust_ci (macos-latest, beta)	52s
rust_ci (windows-latest, stable)	2m 9s
rust_ci (ubuntu-latest, stable)	53s
rust_ci (ubuntu-latest, beta)	52s
rust_ci (windows-latest, beta)	2m 30s
rust_ci (macos-latest, stable)	54s
	8m 10s

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