C++: Set precision to low

There are no barriers, so the query as is will flag up any use of the
identified functions.

Author: jketema

cpp/ql/src/experimental/Security/CWE/CWE-409/DecompressionBombs.ql

@@ -3,7 +3,7 @@
  * @description User-controlled data that flows into decompression library APIs without checking the compression rate is dangerous
  * @kind path-problem
  * @problem.severity error
- * @precision high
+ * @precision low
  * @id cpp/data-decompression-bomb
  * @tags security
  *       experimental