fix(@angular/cli): remove vendorSourceMap warning that vendorSourceMap is not allowed

While the build works and there are no error, at the moment you will have a warning in `angular.json`

Author: alan-agius4

packages/angular/cli/lib/config/schema.json

@@ -605,6 +605,11 @@
               "description": "Output sourcemaps.",
               "default": true
             },
+            "vendorSourceMap": {
+              "type": "boolean",
+              "description": "Resolve vendor packages sourcemaps.",
+              "default": false
+            },
             "evalSourceMap": {
               "type": "boolean",
               "description": "Output in-file eval sourcemaps.",
@@ -1000,6 +1005,11 @@
               "type": "boolean",
               "description": "Output sourcemaps."
             },
+            "vendorSourceMap": {
+              "type": "boolean",
+              "description": "Resolve vendor packages sourcemaps.",
+              "default": false
+            },
             "evalSourceMap": {
               "type": "boolean",
               "description": "Output in-file eval sourcemaps."
@@ -1383,6 +1393,11 @@
               "description": "Output sourcemaps.",
               "default": true
             },
+            "vendorSourceMap": {
+              "type": "boolean",
+              "description": "Resolve vendor packages sourcemaps.",
+              "default": false
+            },
             "evalSourceMap": {
               "type": "boolean",
               "description": "Output in-file eval sourcemaps.",