Fix comma that should have been a semicolon

Didn't cause any problem, but still good to fix. Reported by
keithchugg on github.
diff --git a/celt/celt_lpc.c b/celt/celt_lpc.c
index 90839f4..8ecb693 100644
--- a/celt/celt_lpc.c
+++ b/celt/celt_lpc.c
@@ -107,7 +107,7 @@
    {
       opus_val32 sum[4];
       sum[0] = SHL32(EXTEND32(x[i  ]), SIG_SHIFT);
-      sum[1] = SHL32(EXTEND32(x[i+1]), SIG_SHIFT),
+      sum[1] = SHL32(EXTEND32(x[i+1]), SIG_SHIFT);
       sum[2] = SHL32(EXTEND32(x[i+2]), SIG_SHIFT);
       sum[3] = SHL32(EXTEND32(x[i+3]), SIG_SHIFT);
       xcorr_kernel(rnum, x+i-ord, sum, ord, arch);