Add change note

Author: lcartey

change_notes/2023-03-27-integer-overflow.md

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+ * `A4-7-1` - `IntegerExpressionLeadToDataLoss.ql` - reduce false positives and false negatives by:
+   - Identifying additional categories of valid guard.
+   - Excluding guards which were not proven to prevent overflow or underflow.
+   - Expand coverage to include unary operations and arithmetic assignment operations.