Java: Fix bug in matching generic signatures.

Author: aschackmull

java/ql/src/semmle/code/java/dataflow/ExternalFlow.qll

@@ -561,7 +561,7 @@ private RefType interpretType(string namespace, string type, boolean subtypes) {
 private string paramsStringPart(Callable c, int i) {
   i = -1 and result = "("
   or
-  exists(int n, string p | c.getParameterType(n).toString() = p |
+  exists(int n, string p | c.getParameterType(n).getErasure().toString() = p |
     i = 2 * n and result = p
     or
     i = 2 * n - 1 and result = "," and n != 0