tslint - Missing trailing comma (trailing-comma) on the last line

Include trailing comma even in the last line is a good practice of having less merge conflict, although it looks weird.

You clearly have the rule enabled for multi-line objects:

"trailing-comma": [true, {
  "singleline": "never",
  "multiline": {
    "objects": "always",     // <==================
    "arrays": "always",
    "functions": "never",
    "typeLiterals": "ignore"
  }
}]

So...disable it by making that "never" (if you want to disallow commas there) or "ignore" (if you want to allow commas to be there or not, either way).