fate: readjust AAC encoder TNS test

The recent commits change the value slightly. Even though it's
within the threshold it's better to risk as little as possible
especially when different systems, processors, FPUs and compilers
are involved.

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 = 648.50
+fate-aac-tns-encode: CMP_TARGET = 648.80
 fate-aac-tns-encode: FUZZ = 2.8
 fate-aac-tns-encode: SIZE_TOLERANCE = 3560