fix annoying lint rule

Author: slorber

tslint.json

@@ -11,7 +11,8 @@
     "quotemark": [true, "single", "jsx-double"],
     "ordered-imports": false,
     "object-literal-sort-keys": false,
-    "arrow-parens": false,
+    "arrow-parens": [true, "ban-single-arg-parens"],
+    "ter-arrow-parens": false,
     "no-console": [false],
     "no-unused-expression": [true, "allow-fast-null-checks"],
     "comment-format": false,