JS: Move a test failure explanation into the test suite

We have an issue for fixing the underlying problem

Author: asgerf

javascript/ql/lib/semmle/javascript/security/dataflow/UnsafeShellCommandConstructionQuery.qll

@@ -14,8 +14,6 @@ import UnsafeShellCommandConstructionCustomizations::UnsafeShellCommandConstruct
  * A taint-tracking configuration for reasoning about shell command constructed from library input vulnerabilities.
  */
 module UnsafeShellCommandConstructionConfig implements DataFlow::ConfigSig {
-  // TODO: we get a FP in the test case due to SanitizingRegExpTest not being able to generate a barrier edge
-  //       for an edge into a phi node.
   predicate isSource(DataFlow::Node source) { source instanceof Source }
 
   predicate isSink(DataFlow::Node sink) { sink instanceof Sink }

javascript/ql/test/query-tests/Security/CWE-078/UnsafeShellCommandConstruction/lib/lib.js

@@ -250,7 +250,7 @@ module.exports.goodSanitizer = function (name) {
 
 	var cleaned = cleanInput(name);
 
-	cp.exec("rm -rf " + cleaned); // OK
+	cp.exec("rm -rf " + cleaned); // OK - But FP due to SanitizingRegExpTest not being able to generate a barrier edge for an edge into a phi node.
 }
 
 var fs = require("fs");