[clang] [analyzer] Fix core.VLASize checker false positive taint reports (PR #68140)

[via cfe-commits]

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@@ -218,7 +218,7 @@ void VLASizeChecker::reportTaintBug(const Expr *SizeE, ProgramStateRef State,
   SmallString<256> buf;
   llvm::raw_svector_ostream os(buf);
   os << "Declared variable-length array (VLA) ";
-  os << "has tainted size";
+  os << "has a tainted (attacker controlled) size that can be 0 or negative";
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NagyDonat wrote:

```suggestion
  os << "has tainted (attacker controlled) size that can be 0 or negative";
```
I feel that the indefinite article "sounds strange" in this message, because the size of an array is a specific unique value. Another alternative would be "The size of the variable-length array (VLA) is a tainted value that can be 0 or negative" or something similar.

Of course the tests need to be updated if you change this message.

https://github.com/llvm/llvm-project/pull/68140