style: exclude parentheses around sole arrow function parameters

as discussion at: https://github.com/xeptore/commitiquette/pull/1#pullrequestreview-626076153 we
decided to remove prentheses around sole arrow function paraemeters.
a re-linting commit will be issued in the next commit.

Author: xeptore

.prettierrc

@@ -2,5 +2,6 @@
   "singleQuote": true,
   "tabWidth": 2,
   "useTabs": false,
-  "printWidth": 120
+  "printWidth": 120,
+  "arrowParens": "avoid"
 }