JS: Update score and add CWE-730 to LoopBoundInjection

This is a denial-of-service query, but was missing the CWE-730 tag
("denial of service") and consequently had a lower score than the
other DoS queries.

Author: asgerf

javascript/ql/src/Security/CWE-834/LoopBoundInjection.ql

@@ -4,10 +4,11 @@
  *              property can cause indefinite looping.
  * @kind path-problem
  * @problem.severity warning
- * @security-severity 6.5
+ * @security-severity 7.5
  * @id js/loop-bound-injection
  * @tags security
  *       external/cwe/cwe-834
+ *       external/cwe/cwe-730
  * @precision high
  */