style: fix lint violations about unused API

per `ruff check`

Author: 2bndy5

circuitpython_build_tools/build.py

@@ -84,7 +84,7 @@ def get_nested(doc, *args, default=None):
         if doc is None: return default
         try:
             doc = doc[a]
-        except (KeyError, IndexError) as e:
+        except (KeyError, IndexError):
             return default
     return doc
 

circuitpython_build_tools/scripts/build_mpy_cross.py

@@ -25,9 +25,6 @@
 from circuitpython_build_tools import build
 from circuitpython_build_tools import target_versions
 
-import os
-import sys
-
 import click
 
 @click.command