Deprecate `EnsureNode#body` in favour of `EnsureNode#branch` #1201

Job	Run time
Coding Style \| 3.0	39s
Main Gem Specs \| RuboCop: master \| 2.7	1m 50s
Specs \| 2.7	47s
Main Gem Specs \| RuboCop: master \| 3.0	1m 49s
Prism	25s
Main Gem Specs \| RuboCop: v1.61.0 \| 3.3	1m 59s
Specs \| 3.0	31s
Specs \| 3.1	36s
Specs \| 3.2	27s
Specs \| 3.3	23s
Specs \| head	25s
Coverage \| 2.7	44s
Specs "modern" \| 3.0	28s
Specs \| jruby	47s
Specs \| jruby-head	42s
Specs \| truffleruby	56s
Specs \| truffleruby-head	1m 10s
	14m 38s

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