[BUG] Themes have trailing commas

[Webmaster4o]

Some of the built-in themes contain trailing commas and are therefore not valid JSON. Parsing some of Pythonista's themes with the json module will therefore throw an error.

Example from "Oceanic":

"scopes": {
        "default": {
            "color": "#f9f9f5",
        },

The offending comma is the one after the "color" specification, which is invalid.