[refactor] Remove orphaned lowercase-l-suffix check (dead since 2018) (#10876)

The W0332 "lowercase-l-suffix" message was a Python 2-only check
(maxversion: 3.0) that flagged `123l` vs `123L` for long integers.
Its message definition was removed in May 2018 (commit 41d47dd,
"Remove a couple of Python 2 specific checks", closes #1896), but the
check code (`if string.endswith("l")`) survived as dead code — the
unregistered message would fail if it ever triggered, which it can't
since Python 3's tokenizer never produces tokens ending in `l`.

Author: Pierre-Sassoulas

pylint/checkers/format.py

@@ -451,9 +451,6 @@ def process_tokens(self, tokens: list[tokenize.TokenInfo]) -> None:
                         check_equal = False
                         self.check_indent_level(line, indents[-1], line_num)
 
-            if tok_type == tokenize.NUMBER and string.endswith("l"):
-                self.add_message("lowercase-l-suffix", line=line_num)
-
             if string in _KEYWORD_TOKENS:
                 self._check_keyword_parentheses(tokens, idx)