avcodec/cbs_h265_syntax_template: Limit sps_num_palette_predictor_initializer_minus1 to 127

Fixes: index 128 out of bounds for type 'uint16_t [128]'
Fixes: 38651/clusterfuzz-testcase-minimized-ffmpeg_BSF_HEVC_METADATA_fuzzer-6296416058736640

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/cbs_h265_syntax_template.c

@@ -728,7 +728,7 @@ static int FUNC(sps_scc_extension)(CodedBitstreamContext *ctx, RWContext *rw,
 
         flag(sps_palette_predictor_initializer_present_flag);
         if (current->sps_palette_predictor_initializer_present_flag) {
-            ue(sps_num_palette_predictor_initializer_minus1, 0, 128);
+            ue(sps_num_palette_predictor_initializer_minus1, 0, 127);
             for (comp = 0; comp < (current->chroma_format_idc ? 3 : 1); comp++) {
                 int bit_depth = comp == 0 ? current->bit_depth_luma_minus8 + 8
                                           : current->bit_depth_chroma_minus8 + 8;