Correct minor compilation errors in test code

java/ql/test/query-tests/Nullness/B.java

@@ -120,7 +120,7 @@ public class B {
   }
 
   private Object mkMaybe() {
-    if (maybe) throw new Exception();
+    if (maybe) throw new RuntimeException();
     return new Object();
   }
 
@@ -267,7 +267,7 @@ public class B {
     }
     if(msg != null) {
       msg += "foobar";
-      throw new Exception(msg);
+      throw new RuntimeException(msg);
     }
     obj.hashCode(); // OK
   }
@@ -286,7 +286,7 @@ public class B {
 
     int[] b = maybe ? null : new int[iters];
     if (iters > 0 && (b == null || b.length < iters)) {
-      throw new Exception();
+      throw new RuntimeException();
     }
     for (int i = 0; i < iters; ++i) {
       b[i] = 0; // NPE - false positive

java/ql/test/query-tests/Nullness/C.java

@@ -87,7 +87,7 @@ public class C {
         vals[0] = 0; // OK
         break;
       default:
-        throw new Exception();
+        throw new RuntimeException();
     }
   }