FindPython: fix typo error

Fixes: #23476

Modules/FindPython/Support.cmake

@@ -674,7 +674,7 @@ endfunction()
 function (_PYTHON_GET_LAUNCHER _PYTHON_PGL_NAME)
   cmake_parse_arguments (PARSE_ARGV 1 _PGL "INTERPRETER;COMPILER" "" "")
 
-  unset ({_PYTHON_PGL_NAME} PARENT_SCOPE)
+  unset (${_PYTHON_PGL_NAME} PARENT_SCOPE)
 
   if ((_PGL_INTERPRETER AND NOT _${_PYTHON_PREFIX}_EXECUTABLE)
       OR (_PGL_COMPILER AND NOT _${_PYTHON_PREFIX}_COMPILER))