⚡ [pypinyin/style/_utils.py] optimize has_finals with module-level constant (#366)

Move the list of symbols in has_finals to a module-level tuple _NO_FINALS_SYMBOLS.
This avoids creating the list on every function call and allows for slightly
more efficient iteration.

Measured improvement:
Baseline: 0.2752µs per call
After: 0.2795µs per call
The difference is within measurement error, but the change follows best practices
by avoiding repeated allocations and using a constant for iteration.

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
Co-authored-by: mozillazg <485054+mozillazg@users.noreply.github.com>

Author: mozillazg

pypinyin/style/_utils.py

@@ -84,10 +84,13 @@ def replace_symbol_to_no_symbol(pinyin):
     return RE_NUMBER.sub('', value)
 
 
+# 鼻音: 'm̄', 'ḿ', 'm̀', 'ń', 'ň', 'ǹ' 没有韵母
+_NO_FINALS_SYMBOLS = ('m̄', 'ḿ', 'm̀', 'ń', 'ň', 'ǹ')
+
+
 def has_finals(pinyin):
     """判断是否有韵母"""
-    # 鼻音: 'm̄', 'ḿ', 'm̀', 'ń', 'ň', 'ǹ ' 没有韵母
-    for symbol in ['m̄', 'ḿ', 'm̀', 'ń', 'ň', 'ǹ']:
+    for symbol in _NO_FINALS_SYMBOLS:
         if symbol in pinyin:
             return False