C++: Remove redundant lines.

Author: geoffw0

cpp/ql/lib/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasedSSA.qll

@@ -688,11 +688,7 @@ private Overlap getExtentOverlap(MemoryLocation0 def, MemoryLocation0 use) {
     (
       // EntireAllocationMemoryLocation exactly overlaps itself.
       use instanceof EntireAllocationMemoryLocation and
-      (
-        def.getAnAllocation() = use.getAnAllocation() or
-        not exists(def.getAnAllocation()) or
-        not exists(def.getAnAllocation())
-      ) and
+      def.getAnAllocation() = use.getAnAllocation() and
       result instanceof MustExactlyOverlap
       or
       not use instanceof EntireAllocationMemoryLocation and