pybricksdev._vendored.dfu_upload: fix Python 3.11 compatibility

Python 3.11 dropped inspect.getargspec so we are no getting an
AttributeError. This was for Python 2 compatibility, so we can just
removed it and use getfullargspec() exclusively.

Fixes: pybricks/support#973

Author: dlech

CHANGELOG.md

@@ -6,6 +6,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+- Fixed Python 3.11 compatibility of vendored `dfu_upload` module ([support#973]).
+
+[support#973]: https://github.com/pybricks/support/issues/973
+
 ## [1.0.0-alpha.38] - 2023-03-03
 
 ### Added

pybricksdev/_vendored/dfu_upload.py

@@ -83,11 +83,7 @@
 # USB DFU interface
 __DFU_INTERFACE = 0
 
-# Python 3 deprecated getargspec in favour of getfullargspec, but
-# Python 2 doesn't have the latter, so detect which one to use
-getargspec = getattr(inspect, "getfullargspec", inspect.getargspec)
-
-if "length" in getargspec(usb.util.get_string).args:
+if "length" in inspect.getfullargspec(usb.util.get_string).args:
     # PyUSB 1.0.0.b1 has the length argument
     def get_string(dev, index):
         return usb.util.get_string(dev, 255, index)