fate: adjust AAC encoder TNS test target

The new commits improve the quality.
Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>

tests/fate/aac.mak

@@ -172,7 +172,7 @@ fate-aac-tns-encode: CMD = enc_dec_pcm adts wav s16le $(TARGET_SAMPLES)/audio-re
 fate-aac-tns-encode: CMP = stddev
 fate-aac-tns-encode: REF = $(SAMPLES)/audio-reference/luckynight_2ch_44kHz_s16.wav
 fate-aac-tns-encode: CMP_SHIFT = -4096
-fate-aac-tns-encode: CMP_TARGET = 660.85
+fate-aac-tns-encode: CMP_TARGET = 648.50
 fate-aac-tns-encode: FUZZ = 2.8
 fate-aac-tns-encode: SIZE_TOLERANCE = 3560