refactor: simplify docstring for bandpass filtering method

Codes/FTT_autocorrelation/FFT_AutoCorrelation.py

@@ -35,7 +35,7 @@ class TemporalAnalyzer:
         self._setup_bandpass_filter()
         
     def _apply_filter(self, data: np.ndarray) -> np.ndarray:
-        """Zero-phase bandpass filtering"""
+        """bandpass filtering"""
         return signal.filtfilt(self.b, self.a, data)
         
     def _setup_bandpass_filter(self) -> None: