Update dependency deepmerge to v4

Author: renovate[bot]

package.json

@@ -26,7 +26,7 @@
     "@angular/router": "6.1.10",
     "b64-to-blob": "^1.2.19",
     "core-js": "^2.4.1",
-    "deepmerge": "^2.0.1",
+    "deepmerge": "4.2.2",
     "dot-object": "^1.7.0",
     "fabric": "^2.2.4",
     "file-saver": "^1.3.8",