Add the relelase note for v1.46.0

Author: koic

relnotes/v1.46.0.md

@@ -0,0 +1,7 @@
+### New features
+
+* [#379](https://github.com/rubocop/rubocop-ast/pull/379): Support `RuboCop::AST::ComplexNode`. ([@koic][])
+
+### Bug fixes
+
+* [#380](https://github.com/rubocop/rubocop-ast/pull/380): Fix `RuboCop::AST::NumericNode#sign?` to return boolean. ([@viralpraxis][])