remove --mangle-props from fuzzing (#1777)

The inherently unsafe nature makes this feature unsuitable to be tested this way.

fixes #1774

test/ufuzz.json

@@ -13,12 +13,6 @@
             "toplevel": true
         }
     },
-    {
-        "compress": {
-            "warnings": false
-        },
-        "mangleProperties": {}
-    },
     {
         "compress": {
             "warnings": false
@@ -37,23 +31,6 @@
             "bracketize": true
         }
     },
-    {
-        "compress": {
-            "passes": 3,
-            "properties": false,
-            "toplevel": true,
-            "warnings": false
-        },
-        "mangle": {
-            "toplevel": true
-        },
-        "mangleProperties": {
-            "ignore_quoted": true
-        },
-        "output": {
-            "keep_quoted_props": true
-        }
-    },
     {
         "compress": {
             "keep_fargs": false,