Simplify calls to `register_element` #1576

Job	Run time
rubocop	13s
tests (ubuntu-latest, 2.7)	21s
tests (ubuntu-latest, 3.0)	9s
tests (ubuntu-latest, 3.1)	10s
tests (ubuntu-latest, 3.2)	9s
tests (ubuntu-latest, head)	7s
tests (ubuntu-latest, truffleruby-22.2)	34s
tests (ubuntu-latest, truffleruby-22.3)	36s
tests (ubuntu-latest, truffleruby-head)	26s
tests (macos-latest, 2.7)	1m 16s
tests (macos-latest, 3.0)	17s
tests (macos-latest, 3.1)	17s
tests (macos-latest, 3.2)	24s
tests (macos-latest, head)	19s
tests (macos-latest, truffleruby-22.2)	1m 17s
tests (macos-latest, truffleruby-22.3)	1m 21s
tests (macos-latest, truffleruby-head)	57s
	8m 53s

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