Remove irnorm option from afir filter for ffmpeg 6.x compatibility

The irnorm option was added in ffmpeg 7.x. Dropping it makes the
bandpass filter work with Ubuntu's ffmpeg 6.1.1 package without
affecting detection results.

Author: kookster

src/audio.js

@@ -85,7 +85,7 @@ export function bandpassFilter(rawPath, lowFreq, highFreq, sampleRate = SAMPLE_R
       "-i",
       rawPath,
       "-filter_complex",
-      `sinc=hp=${lowFreq}:lp=${highFreq}:r=${sampleRate}[ir];[0:a][ir]afir=irnorm=-1`,
+      `sinc=hp=${lowFreq}:lp=${highFreq}:r=${sampleRate}[ir];[0:a][ir]afir`,
       "-f",
       "s16le",
       "-acodec",