style: remove or ignore unused imports

The following files had unused imports removed:
- `scripts/30k-image.py`
- `scripts/dl_icons.py`
- `scripts/redact-cast.py`

scripts/30k-image.py

@@ -7,7 +7,6 @@ This creates a shareable social media graphic with confetti animation.
 import argparse
 import base64
 import math
-import os
 import random
 from pathlib import Path
 

scripts/dl_icons.py

@@ -3,7 +3,6 @@
 Download Material Design Icons SVGs used in the README and save to local assets.
 """
 
-import os
 from pathlib import Path
 
 import requests

scripts/redact-cast.py

@@ -1,7 +1,5 @@
 #!/usr/bin/env python3
 import json
-import os
-import re
 import sys
 
 import pyte