avfilter/af_volumedetect: use log10 instead of hardcoded constant

This is likely more precise and conveys the intent better.
Reviewed-by: Mark Harris <mark.hsj@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>

libavfilter/af_volumedetect.c

@@ -78,7 +78,7 @@ static inline double logdb(uint64_t v)
     double d = v / (double)(0x8000 * 0x8000);
     if (!v)
         return MAX_DB;
-    return log(d) * -4.3429448190325182765112891891660508229; /* -10/log(10) */
+    return -log10(d) * 10;
 }
 
 static void print_stats(AVFilterContext *ctx)