Add change note

Author: smowton

java/ql/src/change-notes/2022-04-01-switch-rule-expressions.md

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+---
+category: minorAnalysis
+---
+* The `SwitchCase.getRuleExpression()` predicate now gets expressions for case rules with an expression on the right-hand side of the arrow belonging to both `SwitchStmt` and `SwitchExpr`, and the corresponding `getRuleStatement()` no longer returns an `ExprStmt` in either case. Previously `SwitchStmt` and `SwitchExpr` behaved differently in 
+this respect.