Fix typo in bin launching stub for wheels

Description

Fix typo introduced by !2052 (merged).

API Changes and Justification

Backwards Compatible Changes

• This change does not modify any class/function/struct/type definitions in a public C header file or any Python class/function definitions
• This change adds new classes/functions/structs/types to a public C header file or Python module

Backwards Incompatible Changes

• This change modifies an existing class/function/struct/type definition in a public C header file or Python module
• This change removes an existing class/function/struct/type from a public C header file or Python module

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wheel/setup.py.in

@@ -74,7 +74,7 @@ try:
     from importlib.resources import files, as_file
 except ImportError:  # FIXME: Python < 3.9
     from importlib_resources import files, as_file
-with as_file(files('lalapps') / 'bin' / {}) as path:
+with as_file(files('lalapps') / 'bin' / '{}') as path:
     os.execv(path, sys.argv)
 """