[lldb][test][Shell] Remove Python 2 compatibility in build.py (llvm#163192)

_winreg was renamed to winreg in 3.0, and we require >= 3.8.

https://docs.python.org/3/whatsnew/3.0.html#library-changes

Author: DavidSpickett

lldb/test/Shell/helper/build.py

@@ -9,12 +9,8 @@
 import sys
 
 if sys.platform == "win32":
-    # This module was renamed in Python 3.  Make sure to import it using a
-    # consistent name regardless of python version.
-    try:
-        import winreg
-    except:
-        import _winreg as winreg
+    import winreg
+
 
 if __name__ != "__main__":
     raise RuntimeError("Do not import this script, run it instead")