Format emit.ml (#3831)

Author: gretay-js

backend/.ocamlformat-enable

@@ -1,11 +1,14 @@
+; CR-soon gyorsh: format all files under arm64/amd64
 amd64/cfg_selection.ml
+amd64/emit.ml
 amd64/selection.ml
 amd64/selection_utils.ml
 amd64/simd*.ml
 amd64/stack_check.ml
 amd64/stack_class.ml
 amd64/vectorize_specific.ml
 arm64/cfg_selection.ml
+arm64/emit.ml
 arm64/selection.ml
 arm64/selection_utils.ml
 arm64/simd*.ml