fix: the del-cleanup lines still referenced the renamed imports

The pkg_resources -> importlib.metadata change renamed the imports but
missed the cleanup three lines below, which still did
`del get_distribution` — so `import vpython` raised NameError on every
platform, and the whole matrix went red on the previous push.

Caught by that CI run. The local check that let it through was a syntax
parse, which `del wrong_name` passes; the block is now verified by
executing it, which is what should have happened the first time.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01G7y9rTA1r8r8EhEnPSQenR

Author: sspickle

vpython/__init__.py

@@ -13,8 +13,8 @@
 __gs_version__ = glowscript_version()
 
 del glowscript_version
-del get_distribution
-del DistributionNotFound
+del _dist_version
+del PackageNotFoundError
 
 # Keep the remaining imports later to  ensure that __version__ and
 #  __gs_version__ exist before importing vpython, which itself imports