gnulib-tool.py: Ignore 'use-dict-literal' warnings. * pygnulib/.pylintrc: Don't emit warning messages suggesting that 'dict()' be converted to '{}'. This literal can be mistaken for sets, see discussion here: <https://lists.gnu.org/archive/html/bug-gnulib/2024-04/msg00054.html> * pygnulib/main.py: Document this convention in coding style section. * pygnulib/GLFileSystem.py (GLFileAssistant.__init__): Convert an occurrence of '{}' to 'dict()'.