Warn about deprecated element methods #1587

Job	Run time
rubocop	19s
tests (ubuntu-latest, 2.7)	22s
tests (ubuntu-latest, 3.0)	8s
tests (ubuntu-latest, 3.1)	10s
tests (ubuntu-latest, 3.2)	9s
tests (ubuntu-latest, head)	8s
tests (ubuntu-latest, truffleruby-22.2)	36s
tests (ubuntu-latest, truffleruby-22.3)	35s
tests (ubuntu-latest, truffleruby-head)	28s
tests (macos-latest, 2.7)	1m 10s
tests (macos-latest, 3.0)	24s
tests (macos-latest, 3.1)	20s
tests (macos-latest, 3.2)	18s
tests (macos-latest, head)	14s
tests (macos-latest, truffleruby-22.2)	1m 14s
tests (macos-latest, truffleruby-22.3)	1m 1s
tests (macos-latest, truffleruby-head)	49s
	8m 25s

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