Move type-checking imports into type-checking block

Author: hugovk

Diff for: build_docs.py

@@ -33,7 +33,6 @@
 import sys
 from argparse import ArgumentParser, Namespace
 from bisect import bisect_left as bisect
-from collections.abc import Iterable, Sequence
 from contextlib import contextmanager, suppress
 from dataclasses import dataclass
 from datetime import datetime as dt
@@ -51,6 +50,10 @@
 import urllib3
 import zc.lockfile
 
+TYPE_CHECKING = False
+if TYPE_CHECKING:
+    from collections.abc import Iterable, Sequence
+
 try:
     from os import EX_OK
     from os import EX_SOFTWARE as EX_FAILURE