Remove unused `ostruct` #114

Job	Run time
Ruby 2.4 - macos-latest	6s
Ruby 2.5 - macos-latest	6s
Ruby 2.6 - macos-latest	35s
Ruby 2.7 - macos-latest	34s
Ruby 3.0 - macos-latest	22s
Ruby 3.1 - macos-latest	22s
Ruby 3.2 - macos-latest	20s
Ruby 3.3 - macos-latest	36s
Ruby head - macos-latest	20s
Ruby jruby - macos-latest	36s
Ruby jruby-head - macos-latest	36s
Ruby truffleruby - macos-latest	50s
Ruby 2.4 - ubuntu-20.04	28s
Ruby 2.5 - ubuntu-20.04	32s
Ruby 2.6 - ubuntu-20.04	33s
Ruby 2.7 - ubuntu-20.04	31s
Ruby 3.0 - ubuntu-20.04	22s
Ruby 3.1 - ubuntu-20.04	20s
Ruby 3.2 - ubuntu-20.04	22s
Ruby 3.3 - ubuntu-20.04	30s
Ruby head - ubuntu-20.04	15s
Ruby jruby - ubuntu-20.04	51s
Ruby jruby-head - ubuntu-20.04	52s
Ruby truffleruby - ubuntu-20.04	59s
Ruby mingw - windows-latest	1m 33s
Ruby mswin - windows-latest	2m 16s
Ruby jruby - windows-latest	3m 35s
Ruby head - ubuntu-22.04	16s
Ruby 3.1 - ubuntu-22.04	22s
Ruby 3.2 - ubuntu-22.04	19s
Ruby 3.3 - ubuntu-22.04	29s
	20m 48s

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