fix: move comment to relevant lines

pyxform/parsing/expression.py

@@ -74,7 +74,6 @@ def tokenizer(scan, value) -> ExpLexerToken | str:
     return re.Scanner(lexicon)
 
 
-# Scanner takes a few 100ms to compile so use this shared instance.
 class ExpLexerToken:
     __slots__ = ("name", "value", "start", "end")
 
@@ -85,6 +84,7 @@ def __init__(self, name: str, value: str, start: int, end: int) -> None:
         self.end: int = end
 
 
+# Scanner takes a few 100ms to compile so use these shared instances.
 _EXPRESSION_LEXER = get_expression_lexer()
 _TOKEN_NAME_LEXER = get_expression_lexer(name_only=True)